View source for Forensic biology

{{short description|Forensic application of the study of biology}}
{{Copy edit|date=May 2023}}

'''Forensic biology''' is the use of [[biological]] principles and techniques in the context of law enforcement investigations.<ref>{{Cite web |title=Forensic Biology {{!}} Forensic Science |url=https://forensic.unl.edu/forensic-biology |access-date=2023-06-08 |website=forensic.unl.edu}}</ref><ref name=":0">{{Cite book |last1=Houck |first1=Max |title=Fundamentals of Forensic Science |last2=Siegal |first2=Jay |publisher=Academic Press |year=2006 |isbn=978-0-12-356762-8 |location=China}}</ref> 

Forensic biology mainly focuses on [[DNA sequencing]] of biological matter found at crime scenes.<ref>{{Cite web |title=Forensic Biology |url=https://www.cfsre.org/research/forensic-biology#:~:text=Forensic%20Biology%20involves%20the%20analysis,purpose%20of%20identification%20and%20individualization. |access-date=2023-08-31 |website=www.cfsre.org}}</ref> This assists investigators in identifying potential suspects or unidentified bodies. Forensic biology has many sub-branches, such as [[forensic anthropology]], [[forensic entomology]], [[forensic odontology]], [[forensic pathology]], and [[forensic toxicology]].{{Forensic science|physio}}

==Disciplines==
=== History ===
The first recorded use of forensic procedures dates back to the 7th century, when the concept of utilizing fingerprints as a means of identification was first established.<ref>{{Cite web |title=Origins of Forensic Science |url=https://www.crimemuseum.org/crime-library/forensic-investigation/origins-of-forensic-science/ |access-date=2023-05-31 |website=Crime Museum |language=en-US}}</ref>

By the 7th century, forensic procedures were used to account criminals of guilt charges among other things.<ref>{{cite web |title=ORIGINS OF FORENSIC SCIENCE |url=https://www.crimemuseum.org/crime-library/forensic-investigation/origins-of-forensic-science/#:~:text=Although%20it%20is%20uncertain%20exactly,%2C%E2%80%9D%20printed%20in%20that%20period |website=CrimeMuseum.Org |publisher=Crime Museum |access-date=4 March 2022}}</ref><ref>{{Cite web |last=admin |date=2017-12-29 |title=How Forensic Science has Evolved Over Time |url=https://ifflab.org/history-of-forensic-science/ |access-date=2023-05-31 |website=IFF Lab |language=en-US}}</ref>

Nowadays, the practice of autopsies and forensic investigations has seen a significant surge in both public interest and technological advancements. One of the early pioneers in employing these methods, which would later evolve into the field of forensics, was [[Alphonse Bertillon]], who is also known as the "'''father of criminal identification"'''.<ref>{{Cite web |last=lepontissalien |date=2019-05-04 |title=ALPHONSE BERTILLON: THE FATHER OF CRIMINAL IDENTIFICATION |url=https://tracesdefrance.fr/2019/05/04/alphonse-bertillon-the-father-of-criminal-identification/ |access-date=2023-06-08 |website=TRACES DE FRANCE |language=fr-FR}}</ref> In 1879, he introduced a scientific approach to personal identification by developing the science of [[anthropometry]].<ref>{{Cite web |last=CPHS |date=2020-04-07 |title=Criminal Identification: The Bertillon System |url=https://www.clevelandpolicemuseum.org/historical/criminal-identification-the-bertillion-system/ |access-date=2023-06-08 |website=Cleveland Police Museum |language=en-US}}</ref><ref>{{Cite web |last=Tietz |first=Tabea |date=2021-04-23 |title=Alphonse Bertillon's Anthropometric Identification System {{!}} SciHi Blog |url=http://scihi.org/alphonse-bertillon/ |access-date=2023-06-08 |language=en-US}}</ref><ref>{{Cite web |date=2022-09-26 |title=Anthropometry {{!}} NIOSH {{!}} CDC |url=https://www.cdc.gov/niosh/topics/anthropometry/default.html |access-date=2023-05-05 |website=www.cdc.gov |language=en-us}}</ref> This method involved a series of body measurements for distinguishing one human individual from another.

[[Karl Landsteiner]] later made further significant discoveries in forensics.<ref>{{Cite web |title=The Nobel Prize in Physiology or Medicine 1930 |url=https://www.nobelprize.org/prizes/medicine/1930/landsteiner/facts/ |access-date=2023-05-05 |website=NobelPrize.org |language=en-US}}</ref> In 1901, he found out that blood could be categorized into different groups: A, B, AB, and O,<ref>{{Cite journal |last1=FARHUD |first1=Dariush D |last2=ZARIF YEGANEH |first2=Marjan |date=2013-01-01 |title=A Brief History of Human Blood Groups |journal=Iranian Journal of Public Health |volume=42 |issue=1 |pages=1–6 |issn=2251-6085 |pmc=3595629 |pmid=23514954}}</ref> and thus [[Blood compatibility testing|blood typing]] was introduced to the world of crime-solving.<ref>{{Cite web |title=ABO Blood Type Identification and Forensic Science (1900-1960) {{!}} The Embryo Project Encyclopedia |url=https://embryo.asu.edu/pages/abo-blood-type-identification-and-forensic-science-1900-1960 |access-date=2023-05-05 |website=embryo.asu.edu}}</ref>

[https://forensicfield.blog/leone-lattes/ Dr Leone Lattes], a professor at the Institute of Forensic Medicine in Turin, Italy,<ref>{{Cite web |title=Leone Lattes |url=https://prezi.com/lei3xj6ojatr/leone-lattes/ |access-date=2023-05-06 |website=prezi.com |language=en}}</ref><ref>{{Cite news |author=Staff Writer |date=2015-08-04 |title=Who Is Leone Lattes in Forensics? |url=https://www.reference.com/science-technology/leone-lattes-forensics-361fd6aae4403986 |access-date=2023-05-06 |website=Reference.com |language=en-US}}</ref> has made significant additions into forensics as well. In 1915, he discovered a method to determine the blood group of dried bloodstains, which marked a significant advancement from prior techniques limited to analyzing liquid blood. This technique was adopted for criminal investigation.<ref>{{Cite web |date=2022-02-21 |title=Leone Lattes - Forensic's blog |url=https://forensicfield.blog/leone-lattes/ |access-date=2023-05-06 |website=forensicfield.blog |language=en-GB}}</ref><ref>{{Cite web |author=Staff Writer |date=2015-08-04 |title=What Are Leone Lattes's Contributions to Forensic Science? |url=https://www.reference.com/science-technology/leone-lattes-s-contributions-forensic-science-7847395a48f022c8 |access-date=2023-05-06 |website=Reference.com |language=en-US}}</ref>

In 1928, [[Albrecht Hofmann|Albrecht. H.O]], a German chemist, developed a chemical solution [[luminol]], which can be used to detect trace amounts of [[Blood|blood stains]] at [[Crime scene|crime scenes]].<ref>{{Cite web |last=Harris |first=Tom |date=2002-06-11 |title=How Luminol Works |url=https://science.howstuffworks.com/luminol.htm |access-date=2023-06-08 |website=HowStuffWorks |language=en-us}}</ref><ref>{{Cite web |title=Luminol Test {{!}} Howtosmile |url=https://www.howtosmile.org/resource/luminol-test |access-date=2023-06-08 |website=www.howtosmile.org}}</ref>

Among others, [[Alec Jeffreys|Sir Alec Jeffreys]] further shaped forensics into what we know now. In 1984, he developed the [[DNA profiling|DNA fingerprinting]] technique to examine the variations in the genetic code. This can be used to distinguish one individual from another. This method has become important in [[forensic science]] to assist police detective work, and it has also proved useful in resolving paternity and immigration disputes.<ref>{{Cite web |title=Desert Island Discs - Alec Jeffreys - BBC Sounds |url=https://www.bbc.co.uk/sounds/play/b008fcdz |access-date=2023-05-06 |website=www.bbc.co.uk |language=en-GB}}</ref>

In 1983, [[Kary Mullis|Kary B. Mullis]] made a significant contribution to the fields of medicine and criminology  by developing the [[Polymerase chain reaction|PCR]] ([[polymerase chain reaction]]) technique, which can amplify even trace amount of DNA segments in-vitro.<ref>{{Cite web |title=The Nobel Prize in Chemistry 1993 |url=https://www.nobelprize.org/prizes/chemistry/1993/mullis/facts/ |access-date=2023-06-08 |website=NobelPrize.org |language=en-US}}</ref> Such DNA samples, often found in crime scenes in minute amounts, degraded states and sometimes mixed with various body fluids from multiple individuals, can be effectively amplified using PCR. Beyond forensics, PCR has been applied to a wide range of fields, including disease diagnosis and virus detection.<ref>{{cite web |last1=Kanojia |first1=Shikha |title=Forensic Biology {{!}} Sub-Fields {{!}} Significance & Application |url=https://sciencemonk.com/forensic-biology-significance-and-application/ |website=Science Monk|date=11 August 2019 }}</ref>

===DNA analysis===
{{ main | Forensic DNA analysis}}
[[DNA|DNA, or deoxyribonucleic acid]], is one of the most popular pieces of evidence to recover at a crime scene.<ref name=":1">{{Cite book |last1=Fisher |first1=Barry A. J. |title=Techniques of Crime Scene Investigation |last2=Fisher |first2=David R. |publisher=CRC Press |year=2012 |isbn=978-1-4398-1005-7 |location=Boca Raton, Florida}}</ref> More often than not, evidence containing DNA is regarded as ''[[biological evidence]]''.<ref>{{Cite web |date=2021-07-09 |title=Role of DNA in Forensic Science |url=https://www.azolifesciences.com/article/Role-of-DNA-in-Forensic-Science.aspx |access-date=2023-05-06 |website=News-Medical.net |language=en}}</ref> With all of the substantial advances that have been made regarding DNA, biological evidence is recognized to be the "golden standard" in forensic science.<ref>{{Citation |last1=Hicks |first1=T. |title=Forensic DNA Evidence |date=2009 |url=https://doi.org/10.1007/978-0-387-73003-5_106 |encyclopedia=Encyclopedia of Biometrics |pages=573–579 |editor-last=Li |editor-first=Stan Z. |access-date=2023-06-08 |place=Boston, MA |publisher=Springer US |language=en |doi=10.1007/978-0-387-73003-5_106 |isbn=978-0-387-73003-5 |last2=Coquoz |first2=R. |editor2-last=Jain |editor2-first=Anil}}</ref><ref>{{Cite web |title=DNA Evidence: Basics of Identifying, Gathering and Transporting |url=https://nij.ojp.gov/topics/articles/dna-evidence-basics-identifying-gathering-and-transporting |access-date=2023-05-06 |website=National Institute of Justice |language=en}}</ref>

At the scene, biological evidence must be initially visibly recognized. Sometimes this is not always possible and the aid of an alternative light source, or [[Advanced Light Source]] (ALS), is required.<ref>{{Cite web |title=ALS Sheds a Different Light on Crime Scenes {{!}} Office of Justice Programs |url=https://www.ojp.gov/ncjrs/virtual-library/abstracts/als-sheds-different-light-crime-scenes |access-date=2023-06-08 |website=www.ojp.gov}}</ref><ref>{{Cite web |title=Alternate Light Sources {{!}} Forensics {{!}} Forensic Supplies {{!}} Sirchie |url=https://www.sirchie.com/forensics/alternate-light-sources.html |access-date=2023-06-08 |website=www.sirchie.com}}</ref> Once identified as a potential source, presumptive tests are conducted to establish the possibility of the specified biological presence (semen, saliva, blood, urine, etc.).<ref name=":1" /> If positive, samples are collected and submitted for analysis in the laboratory, where confirmatory tests and further tests are performed.<ref name=":0" /><ref name=":1" />

[[DNA Analysis|DNA analysis]] has numerous applications such as paternity testing, identifications of unknown human remains, cold case breakthroughs, as well as connecting suspects and/or victims to a piece(s) of evidence, a scene, or to another person (victim or suspect, respectively).<ref name=":1" /><ref>{{Cite journal |last=Butler |first=John M. |date=2015-08-05 |title=The future of forensic DNA analysis |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |language=en |volume=370 |issue=1674 |pages=20140252 |doi=10.1098/rstb.2014.0252 |issn=0962-8436 |pmc=4580997 |pmid=26101278}}</ref><ref>{{Cite journal |last=Singh |first=Lalji |date=1991 |title=DNA profiling and its applications |url=https://www.jstor.org/stable/24099013 |journal=Current Science |volume=60 |issue=9/10 |pages=580–585 |jstor=24099013 |issn=0011-3891}}</ref><ref>{{Cite journal |last=Saad |first=Rana |date=April 2005 |title=Discovery, development, and current applications of DNA identity testing |journal=Proceedings (Baylor University. Medical Center) |volume=18 |issue=2 |pages=130–133 |doi=10.1080/08998280.2005.11928051 |issn=0899-8280 |pmc=1200713 |pmid=16200161}}</ref> Nuclear DNA evidence can be recovered from [[blood]], [[semen]], [[saliva]], [[epithelial cells]] and [[hair]] (if the root is still intact).<ref name=":1" /> Furthermore, [[Mitochondrial DNA|Mitochondrial DNA (mt DNA)]] can be recovered from the shaft of hair, [[bone]] and the roots of [[teeth]].

For most forensic DNA samples, [[STR analysis]] of [[Autosome|autosomal]] [[Microsatellite|short tandem repeats (STR)]] is performed in an attempt to individualize the sample to one person with a high degree of statistical confidence.<ref name=":2">{{Cite book|title=Using DNA to Solve Cold Cases|last=National Institute of Justice|first=Office of Justice Programs|date=July 2002}}</ref><ref>{{Cite web |title=What Is STR Analysis? |url=https://nij.ojp.gov/topics/articles/what-str-analysis |access-date=2023-06-08 |website=National Institute of Justice |language=en}}</ref><ref>{{Cite journal |last1=Wyner |first1=Nicole |last2=Barash |first2=Mark |last3=McNevin |first3=Dennis |date=2020 |title=Forensic Autosomal Short Tandem Repeats and Their Potential Association With Phenotype |journal=Frontiers in Genetics |volume=11 |page=884 |doi=10.3389/fgene.2020.00884 |pmid=32849844 |pmc=7425049 |issn=1664-8021 |doi-access=free }}</ref><ref>{{Cite journal |last1=Nwawuba Stanley |first1=Udogadi |last2=Mohammed Khadija |first2=Abdullahi |last3=Bukola |first3=Adams Tajudeen |last4=Omusi Precious |first4=Imose |last5=Ayevbuomwan Davidson |first5=Esewi |date=July 2020 |title=Forensic DNA Profiling: Autosomal Short Tandem Repeat as a Prominent Marker in Crime Investigation |journal=The Malaysian Journal of Medical Sciences |volume=27 |issue=4 |pages=22–35 |doi=10.21315/mjms2020.27.4.3 |issn=1394-195X |pmc=7444828 |pmid=32863743}}</ref> Here, STR markers for autosomal STR are used in forensic [[Dna Typing|DNA typing]] to track down the missing, verify family connections, and potentially connect suspects to crime sites.<ref>{{Cite journal |last1=Keerti |first1=Akshunna |last2=Ninave |first2=Sudhir |last3=Keerti |first3=Akshunna |last4=Ninave |first4=Sudhir |date=2022-10-12 |title=DNA Fingerprinting: Use of Autosomal Short Tandem Repeats in Forensic DNA Typing |journal=Cureus |language=en |volume=14 |issue=10 |pages=e30210 |doi=10.7759/cureus.30210 |doi-access=free |pmid=36381887 |pmc=9650913 |issn=2168-8184}}</ref>

[[File:TaqMan Probes.jpg|thumb|TaqMan Probes]][[File:STR electropherogram of a three person mixture.jpg|thumb|STR electropherogram of a three-person mixture]]
Laboratory analysis of DNA evidence involves the sample DNA being [[DNA extraction|extracted]], quantified, amplified, and visualized. There are several methods of DNA extraction possible including [[Phenol-chloroform extraction|organic (phenol-chloroform) extraction]], [[Chelex 100|Chelex]] extraction,<ref>{{Citation |last=Gautam |first=Akash |title=DNA Isolation by Chelex Method |date=2022 |url=https://doi.org/10.1007/978-3-030-94230-4_10 |work=DNA and RNA Isolation Techniques for Non-Experts |pages=79–84 |editor-last=Gautam |editor-first=Akash |access-date=2023-06-08 |series=Techniques in Life Science and Biomedicine for the Non-Expert |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-94230-4_10 |isbn=978-3-030-94230-4}}</ref> and [[differential extraction]].

Quantitation is commonly conducted using a form of the [[polymerase chain reaction]], known as [[Real-time polymerase chain reaction|real-time PCR]], [[Quantitative PCR|quantitative PCR (qPCR)]].<ref name="ReferenceA">{{cite journal |last1=Higuchi |first1=R. |last2=Fockler |first2=C. |last3=Dollinger |first3=G. |last4=Watson |first4=R. |title=Kinetic PCR analysis: real-time monitoring of DNA amplification reactions |journal=Bio/Technology |date=1993 |volume=11 |issue=9 |pages=1026–1030 |doi=10.1038/nbt0993-1026|pmid=7764001 |s2cid=5714001 }}</ref><ref name="ReferenceB">{{cite journal |last1=Higuchi |first1=R. |last2=Dollinger |first2=G. |last3=Walsh |first3=P.S. |last4=Griffith |first4=R. |title=Simultaneous amplification and detection of specific DNA sequences |journal=Bio/Technology |date=1992 |volume=10 |issue=4 |pages=413–417 |doi=10.1038/nbt0492-413|pmid=1368485 |s2cid=1684150 }}</ref> qPCR is the preferred method of DNA quantitation for forensic cases because it is very precise, human-specific, qualitative, and quantitative.<ref name="Elsevier">{{cite book |last1=Butler |first1=John |title=Forensic DNA Typing: Biology, Technology, and Genetics of STR Markers |date=2005 |publisher=Elsevier |location=Burlington, MA, USA |isbn=978-0-12-147952-7 |pages=75–79 |edition=2}}</ref><ref>{{Cite web |title=Choosing the Right Method for Nucleic Acid Quantitation |url=https://www.promega.com/resources/pubhub/choosing-the-right-method-for-nucleic-acid-quantitation/ |access-date=2023-06-08 |website=www.promega.com}}</ref> This technique analyses changes in fluorescence signals of amplified DNA fragments between each PCR cycle without needing to pause the reaction or open the temperature-sensitive PCR tubes.<ref name="Elsevier" /> In addition to the components necessary for standard a PCR reaction (i.e. template DNA, carefully designed forward and reverse [[Primer (molecular biology)|primers]], [[DNA polymerase]] [usually ''[[Taq polymerase|Taq]]''], [[Nucleoside triphosphate|dNTPs]], and a buffer solution containing Mg2+), qPCR reactions involve fluorescent dye-labelled [[Hybridization probe|probes]] that complement and anneal to the DNA sequence of interest that lies between the two primers.<ref name="Elsevier" /> A "reporter" (R) dye is attached at the 5’ end of the fluorescent probe, while a "quencher" (Q) dye is attached at the 3’ end. Before the DNA strands are extended by the polymerase, the reporter and quencher are close enough in space that no fluorescence is detected by the [[Quantitative PCR instrument|instrument]] (the quencher completely absorbs/masks the fluorescence of the reporter). As the polymerase begins to extend the strand, the 5' end of the probe is degraded by the polymerase due to its [[exonuclease]] activity. The reporter dye is released from the 5’ end. It is no longer quenched, thus enabling fluorescence detection.<ref name="ReferenceA" /><ref name="ReferenceB" /> A graph is constructed for the sample DNA comparing the presence of fluorescence (y-axis) to cycle number (x-axis) of the qPCR process. This is then compared to a standard curve of the cycle fluorescence threshold (y-axis) versus the log of known DNA concentrations (x-axis).<ref>{{cite book |last1=Butler |first1=John |title=Forensic DNA Typing: Biology, Technology, and Genetics of STR Markers |date=2005 |publisher=Elsevier |location=Burlington, MA, USA |isbn=978-0-12-147952-7 |page=78 |edition=2}}</ref> By comparing the sample data to the standard curve, one may extrapolate the DNA concentration in the sample, which is essential to move forward with PCR amplification and [[capillary electrophoresis]] to obtain a [[genetic fingerprinting|DNA profile]]. DNA profiles are produced as an [[electropherogram]]. The obtained profile can be compared to known samples in [[CODIS]] to identify a possible suspect.<ref name=":0" /> Based on known frequencies of the [[genotype]] found in the DNA profile, the DNA analyst may place a statistical measure of confidence on DNA match.<ref>{{cite book |last1=Butler |first1=John |title=Advanced Topics in Forensic DNA Typing: Interpretation |date=2015 |publisher=Academic Press |location=Oxford, UK |isbn=978-0-12-405213-0 |pages=213–444}}</ref>

==== Mitochondrial DNA analysis ====
[[Mitochondrial DNA]] (mtDNA) is used<ref>{{Cite web |last=Gopalakrishnan |first=Anupama |date=2015-02-25 |title=Mitochondrial DNA Typing in Forensics |url=https://www.promegaconnections.com/mitochondrial-dna-typing-in-forensics/ |access-date=2023-06-08 |website=Promega Connections |language=en-US}}</ref> instead of [[nuclear DNA]] when forensic samples have been degraded, are damaged, or are in very small quantities. In many cases, there may be older human remains, sometimes ancient, and the only options for DNA collection are the body's bone, teeth, or hair.<ref name=":3">{{Cite book|title=Forensic DNA Typing: Biology, Technology, and Genetics of STR Markers, Second Edition|last=Butler|first=John|publisher=Elsevier Academic Press|year=2005|isbn=978-0121479527|location=London, UK|pages=241–288}}</ref>

mtDNA can be extracted from such degraded samples since its presence in cells is much higher than nuclear DNA. There can be more than 1,000 copies of mtDNA in a cell,<ref>{{Cite journal |last1=Zhang |first1=Yanfang |last2=Qu |first2=Yiping |last3=Gao |first3=Ke |last4=Yang |first4=Qi |last5=Shi |first5=Bingyin |last6=Hou |first6=Peng |last7=Ji |first7=Meiju |date=2015-02-15 |title=High copy number of mitochondrial DNA (mtDNA) predicts good prognosis in glioma patients |journal=American Journal of Cancer Research |volume=5 |issue=3 |pages=1207–1216 |issn=2156-6976 |pmc=4449448 |pmid=26045999}}</ref> while there are only two copies of nuclear DNA.<ref name=":3" /> Nuclear DNA is inherited from both the mother and the father but mtDNA is passed down from only the mother to all of her offspring.<ref>{{Cite journal |last1=Luo |first1=Shiyu |last2=Valencia |first2=C. Alexander |last3=Zhang |first3=Jinglan |last4=Lee |first4=Ni-Chung |last5=Slone |first5=Jesse |last6=Gui |first6=Baoheng |last7=Wang |first7=Xinjian |last8=Li |first8=Zhuo |last9=Dell |first9=Sarah |last10=Brown |first10=Jenice |last11=Chen |first11=Stella Maris |last12=Chien |first12=Yin-Hsiu |last13=Hwu |first13=Wuh-Liang |last14=Fan |first14=Pi-Chuan |last15=Wong |first15=Lee-Jun |date=2018-12-18 |title=Biparental Inheritance of Mitochondrial DNA in Humans |journal=Proceedings of the National Academy of Sciences |language=en |volume=115 |issue=51 |pages=13039–13044 |doi=10.1073/pnas.1810946115 |issn=0027-8424 |pmc=6304937 |pmid=30478036 |bibcode=2018PNAS..11513039L |doi-access=free }}</ref><ref name=":3" /> Due to this type of inheritance, mtDNA is useful for identification purposes in forensic work but can also be used for mass disasters, missing persons cases, complex kinship, and genetic genealogy.<ref name=":3" />

The main advantage of using mtDNA is its high copy number.<ref>{{Cite journal |last1=Merheb |first1=Maxime |last2=Matar |first2=Rachel |last3=Hodeify |first3=Rawad |last4=Siddiqui |first4=Shoib Sarwar |last5=Vazhappilly |first5=Cijo George |last6=Marton |first6=John |last7=Azharuddin |first7=Syed |last8=AL Zouabi |first8=Hussain |date=2019-05-09 |title=Mitochondrial DNA, a Powerful Tool to Decipher Ancient Human Civilization from Domestication to Music, and to Uncover Historical Murder Cases |journal=Cells |volume=8 |issue=5 |pages=433 |doi=10.3390/cells8050433 |issn=2073-4409 |pmc=6562384 |pmid=31075917 |doi-access=free }}</ref> However, there are a few disadvantages of using mtDNA as opposed to nuclear DNA. Since mtDNA is inherited maternally and passed to each offspring, all members of the maternal familial line will share a [[haplotype]].<ref name=":4">{{Cite journal|last1=Jobling|first1=Mark A.|last2=Gill|first2=Peter|date=October 2004|title=Correction: Encoded evidence: DNA in forensic analysis|journal=Nature Reviews Genetics|language=En|volume=5|issue=10|pages=739–751|doi=10.1038/nrg1455|pmid=15510165|s2cid=2236821|issn=1471-0056}}</ref> A [[haplotype]] "is a group of alleles in an organism that are inherited together from a single parent". Sharing this haplotype among family members can cause an issue in forensic samples because these samples are often mixtures that contain more than one DNA contributor.<ref name=":3" /> De convolution and interpretation of mtDNA mixtures is more difficult than that of nuclear DNA, and some laboratories choose not to attempt the process<ref>{{Cite journal|url=https://pdfs.semanticscholar.org/36c9/9e996c645ede5c596c692356c6aef1660ff8.pdf?_ga=2.268566321.1937055804.1541653920-1523377491.1541653920|title=Forensic Mitochondrial DNA Analysis: Current Practice and Future Potential|last=Melton|first=T.|date=July 2012|journal=Forensic Science Review|volume=24|issue=2|pages=101–22|doi=10.1201/B15361-17|pmid=26244267|s2cid=10742375|access-date=2018-11-08|archive-date=2018-11-08|archive-url=https://web.archive.org/web/20181108184353/https://pdfs.semanticscholar.org/36c9/9e996c645ede5c596c692356c6aef1660ff8.pdf?_ga=2.268566321.1937055804.1541653920-1523377491.1541653920|url-status=dead}}</ref> Since mtDNA does not recombine, the genetic markers are not as diverse as autosomal STRs are in the case of nuclear DNA.<ref name=":4" /> Another issue is that of [[heteroplasmy]] — when an individual has more than one type of mtDNA in their cells.<ref name=":3" /> This can cause an issue in interpreting data from questioned forensic samples and known samples that contain mtDNA.<ref name=":5">{{Cite journal|last=Melton|first=Terry|date=2004|title=Mitochondrial DNA Heteroplasmy|url=http://mitotyping.com/PDF/MtDNA_Heteroplasmy_Melton_FSR.pdf|journal=Forensic Science Review|volume=16|issue=1|pages=1–20|pmid=26256810}}</ref> Having adequate knowledge and understanding of heteroplasmy can help ensure successful interpretation.<ref name=":5" />

There are some ways to improve success of mtDNA analysis. Preventing contamination at all testing stages and using positive and negative controls is a priority.<ref name=":3" /> In addition, the use of [[Amplicon|mini-amplicons]] can be beneficial. When a sample of mtDNA is severely degraded or has been obtained from an ancient source, the use of small [[amplicon]]s can be used to improve the success of amplification during [[Polymerase chain reaction|PCR]].<ref name=":3" /> In these cases primers amplifying smaller regions of HV1 and HV2 in the control region of mtDNA are used.<ref>{{Cite journal |last1=Erdem |first1=S. |last2=Altunçul |first2=H. |last3=Filoğlu |first3=G. |last4=Ölçen |first4=A. M. |last5=Bülbül |first5=Ö. |date=2011-12-01 |title=Sequencing of mtDNA HV1 and HV2 regions from samples with trace amount of DNA  |journal=Forensic Science International: Genetics Supplement Series |series=Progress in Forensic Genetics 14 |language=en |volume=3 |issue=1 |pages=e455–e456 |doi=10.1016/j.fsigss.2011.09.089 |issn=1875-1768}}</ref> This process has been referred to as the 'ancient DNA' approach.<ref name=":3" />

The first use of mtDNA as evidence in court was in 1996 in ''State of Tennessee v. Paul Ware''.<ref>{{Cite news |agency=Associated Press |date=1996-09-05 |title=A New DNA Test Helps Win a Conviction |language=en-US |work=The New York Times |url=https://www.nytimes.com/1996/09/05/us/a-new-dna-test-helps-win-a-conviction.html |access-date=2023-05-06 |issn=0362-4331}}</ref><ref name=":6">{{Cite web|url=https://www.promega.com/-/media/files/resources/profiles-in-dna/103/mitochondrial-dna-state-of-tennessee-v-paul-ware.pdf?la=en|title=Mitochondrial DNA: State of Tennessee v. Paul Ware|last=Davis|first=C. Leland|date=1998|website=Promega|access-date=November 5, 2018}}</ref> There was only circumstantial evidence against Ware so the admittance of mtDNA from hairs found in the victim's throat and at the scene were key to the case.<ref name=":6" />

In 2004, with the help of the [[National Center for Missing & Exploited Children|National Center for Missing and Exploited Children]] and [[Choicepoint|ChoicePoint]], mtDNA was used to solve a 22-year-old cold case where the nuclear DNA evidence was not originally strong enough.<ref name=":7">{{Cite web|url=http://www.govtech.com/public-safety/DNA-Profiling-Helps-Solve-22-year-old-Murder.html|title=DNA Profiling Helps Solve 22-year-old Murder Case|website=www.govtech.com|date=28 July 2010|language=en|access-date=2018-11-07}}</ref> After mtDNA analysis, Arbie Dean Williams was convicted of the murder of 15-year-old Linda Strait, which had occurred in 1982.<ref name=":7" /><ref>{{Cite web |title=After 24 years, Strait murder resolved {{!}} The Spokesman-Review |url=https://www.spokesman.com/stories/2006/aug/01/after-24-years-strait-murder-resolved/ |access-date=2023-05-06 |website=www.spokesman.com}}</ref>

In 2012, mtDNA evidence allowed investigators to establish a link in a 36-year-old investigation into the [[Oakland County Child Killer|murders of four Michigan children]].<ref name=":8">{{Cite news|url=https://www.cnn.com/2012/07/17/justice/michigan-dna-cold-case/index.html|title=New DNA work may offer break in 36-year-old Michigan slayings |first= Chris |last=Boyette|work=CNN|access-date=2018-11-07}}</ref> Hair fibers found on the bodies of two of the children were tested and the mtDNA found to be the same for each sample. For the investigators this was a big break because it meant that the murders were likely connected.<ref name=":8" />

== Forensic anthropology ==
{{main | Forensic anthropology}}
[[Anthropology]] is applied to forensics most regularly through the collection and analysis of human skeletal remains.<ref name=":0" /><ref>{{Cite web |title=Forensic Anthropology {{!}} Smithsonian National Museum of Natural History |url=http://naturalhistory.si.edu/education/teaching-resources/social-studies/forensic-anthropology |access-date=2023-05-06 |website=naturalhistory.si.edu |language=en}}</ref><ref>{{Cite web |title=Forensic anthropology {{!}} science {{!}} Britannica |url=https://www.britannica.com/science/forensic-anthropology |access-date=2023-05-06 |website=www.britannica.com |language=en}}</ref> The primary goals of anthropological involvement include identification and aiding in scene reconstruction by determining details regarding the circumstances of the victim's death. In cases where conventional techniques<ref name=":9">{{Cite journal |last=Wiersema |first=Jason M. |date=September 2016 |title=Evolution of Forensic Anthropological Methods of Identification |journal=Academic Forensic Pathology |volume=6 |issue=3 |pages=361–369 |doi=10.23907/2016.038 |issn=1925-3621 |pmc=6474555 |pmid=31239912}}</ref> are unable to determine the identity of the remains due to the lack of soft tissue, anthropologists are required to deduce certain characteristics based on the skeletal remains. Race, sex, age and possible ailments can often be determined through bone measurements and looking for clues throughout the skeletal structure.

This becomes necessary when conventional methods that use soft tissue <ref name=":9" /> fail to establish the identity of remains. By examining bone measurements and other skeletal structure characteristics, anthropologists can often determine information such as race, sex, age, and potential health conditions.

== Forensic botany ==
Forensic botany deals with the study of plants, [[Leaf|leaves]], [[seed]]s, and [[pollen]] or plant properties (such as anatomy, growth, behavior, classification, population dynamics, and reproductive cycles) that would be considered as physical evidence.<ref>{{Cite book|url=https://www.taylorfrancis.com/books/9780203484593|title=Forensic Botany|date=2004-09-15|publisher=CRC Press|isbn=978-0-203-48459-3|editor-last=Miller Coyle|editor-first=Heather|edition=0|language=en|doi=10.1201/9780203484593}}</ref><ref>{{Cite web |last=Swetha |date=2020-12-26 |title=Forensic Botany and Its Applications |url=https://legaldesire.com/forensic-botany-and-its-applications/ |access-date=2023-05-06 |website=Legal Desire Media and Insights |language=en-US}}</ref>

Before a plant can aid the investigations, the plant must be identified first to see if it is from the location that the plant was found. Forensic botany can help investigators by providing a link between an individual and the crime scene by pinpointing the geographical location of missing bodies or estimate where the burial took place. Another way that is used is through the interrogation process where investigators compare the traces that the victim(s) are found and compare to the statements of the suspect(s).<ref name="Aquila 2019 920–924">{{Cite journal|last1=Aquila|first1=Isabella|last2=Sacco|first2=Matteo A.|last3=Ricci|first3=Pietrantonio|last4=Gratteri|first4=Santo|date=2019|title=The Role of Forensic Botany in Reconstructing the Dynamics of Trauma from High Falls|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/1556-4029.13934|journal=Journal of Forensic Sciences|language=en|volume=64|issue=3|pages=920–924|doi=10.1111/1556-4029.13934|pmid=30332508|s2cid=52988396|issn=1556-4029}}</ref> Forensic botany can also reveal whether a death is due to suicide, accident, or homicide. Another example of forensic botany aiding investigators is by moss, moss can establish the PMI of a human skeletal, through its growth rate.<ref>{{Cite journal|last1=Longato|first1=S.|last2=Wöss|first2=C.|last3=Hatzer-Grubwieser|first3=P.|last4=Bauer|first4=C.|last5=Parson|first5=W.|last6=Unterberger|first6=S. H.|last7=Kuhn|first7=V.|last8=Pemberger|first8=N.|last9=Pallua|first9=Anton K.|last10=Recheis|first10=W.|last11=Lackner|first11=R.|date=2015-04-07|title=Post-mortem interval estimation of human skeletal remains by micro-computed tomography, mid-infrared microscopic imaging and energy dispersive X-ray mapping|journal=Analytical Methods|volume=7|issue=7|pages=2917–2927|doi=10.1039/c4ay02943g|issn=1759-9660|pmc=4383336|pmid=25878731}}</ref>

For example, an elderly man fell a steep hillside and was found dead. They concluded that the man did not die from the fall but from hypertensive heart disease. Forensic botany concluded that the fall was approximately 10 m and there was a lane that joined the hill path around 9 m perpendicular form the body. It showed he had leaves on his left hand and sweater. There were also broken bushes in the scene. Forensic scientists specializing in forensic botany had grabbed five soil samples and some plant samples from the scene. The plant samples were analyzed through [[Optical microscope|optical microscopy]], and they also examined the victims' clothing since it did carry some plant elements. They did a macroscopic and microscopic analysis compared to the collected samples on the scene. It was concluded that there was no evidence of struggle caused by another person instead, the elderly man had lost his balance.<ref name="Aquila 2019 920–924"/>

=== Subspecialties In Forensic Botany ===
Subdisciplines within forensic botany examples include:

* [[forensic palynology]] (study of pollen and spores). Palynology can produce evidence of decomposition time, location of death or the time of year.
* [[dendrochronology]] (study of the growth of rings of trees stems and roots)
* [[Lichenology]] (study of lichens)
* [[Mycology]] (study of fungi)
* [[Bryology]] (study of bryophytes). Bryology is the easiest to find evidence since bryophyte (a species of plants) attaches to shoes and clothes easily.<ref>{{Cite journal |last1=Margiotta |first1=Gabriele |last2=Bacaro |first2=Giovanni |last3=Carnevali |first3=Eugenia |last4=Severini |first4=Simona |last5=Bacci |first5=Mauro |last6=Gabbrielli |first6=Mario |date=2015-08-01 |title=Forensic botany as a useful tool in the crime scene: Report of a case |url=https://www.sciencedirect.com/science/article/pii/S1752928X15000876 |journal=Journal of Forensic and Legal Medicine |language=en |volume=34 |pages=24–28 |doi=10.1016/j.jflm.2015.05.003 |issn=1752-928X |pmid=26165654 |hdl-access=free |hdl=11368/2840167}}</ref> [[Bryophyte]] useful since even if it is ripped apart or broken down, DNA can still be analyzed. Ways in which DNA can be analyzed is through the [[microscope]] or other sophisticated DNA testing.

== Forensic ornithology ==
Forensic ornithology employs scientific methodologies to ascertain the bird species from traces of evidence such as a small feather, a fragment of bone, or a trace of blood.<ref>{{Cite web |title=Solving Bird Mysteries with Forensic Ornithology - Podcast Episode |url=https://www.scienceofbirds.com/podcast/solving-bird-mysteries-with-forensic-ornithology |access-date=2023-05-06 |website=www.scienceofbirds.com}}</ref> Bird remains can be identified, first and foremost from feathers as feathers exhibit distinctive characteristics specific to a particular bird species, which can be observed both at a macroscopic and microscopic level.

== Forensic odontology ==
{{main | Forensic dentistry}}
Dentistry has helped law enforcement detect and solve cases in criminal and civil proceedings. [[Odontology]] did not get popular until the 1960s when an interest was brought up by the first instructional program in the United States at the [[Armed Forces Institute of Pathology]]. As a result of this program, the term "forensic odontology" is now widely known and understood by both dental and law enforcement professionals.

Odontologists or [[Dentist|dental professionals]] can use dental science to establish a person's identity. The broad duties of a Forensic Odontologist include forensic identification of individuals, including in multi-casualty events, age estimation in living and deceased persons, interpreting injuries in the oral and perioral regions, bite mark analysis and comparison, and assisting forensic pathologists in determining the cause of death if there is a possible contributing dental condition.<ref>{{Cite web |title=Forensic Odontology - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/medicine-and-dentistry/forensic-odontology |access-date=2023-05-06 |website=www.sciencedirect.com}}</ref>

Dental evidence is useful in establishing human identity by comparing the dental features of a deceased person with antemortem dental records.<ref>{{Cite web |title=Encyclopedia of Forensic Sciences, Third Edition |url=http://www.sciencedirect.com:5070/referencework/9780128236789/encyclopedia-of-forensic-sciences-third-edition |access-date=2023-05-06 |website=ScienceDirect |language=en}}</ref>
== Forensic pathology ==
[[Forensic pathology]] is a subfield in forensics where experts examine persons (bodies) who die suddenly, unexpectedly or violently, and thus determine the cause of death.<ref>{{Cite web |title=What is a Forensic Pathologist? |url=https://hsc.unm.edu/omi/about/faq/forensic-pathologist.html |access-date=2023-05-05 |website=hsc.unm.edu}}</ref> The function of a forensic autopsy is to provide information through a postmortem examination of the body and analysis of the fluids to determine the cause of death, manner of death, and mechanism of injury.<ref>{{Cite web |title=Forensic Autopsy - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/medicine-and-dentistry/forensic-autopsy |access-date=2023-05-06 |website=www.sciencedirect.com}}</ref>

A [[Forensic pathology|forensic pathologist]] is a medical doctor who is an expert in both trauma and disease and is responsible for performing autopsies. He/she applies their extensive knowledge of the human body and possible internal and external inflections as he/she performs an autopsy, to ascertain the manner and cause of death hopefully.<ref name=":0" />

Information derived from the autopsy often greatly assists investigative efforts and scene reconstruction.

== Forensic toxicology ==
{{main|Forensic toxicology}}
Forensic toxicology is the use of [[toxicology]] and other disciplines such as [[analytical chemistry]], [[pharmacology]] and [[clinical chemistry]] to aid medical or legal investigation of death, poisoning, and drug use. The primary concern for forensic toxicology is not the legal outcome of the toxicological investigation or the technology utilized but rather the obtainment and interpretation of results.

== Forensic microbiology ==
With recent advances in [[massive parallel sequencing]] (MPS), or [[next-generation sequencing]] (NGS), forensic microbiology has become an increasingly promising area of research. "Initial applications in circumstances of biocrime, bioterrorism and epidemiology use microorganisms for the following reasons: (i) as ancillary evidence in criminal cases; (ii) to clarify causes of death (e.g., drownings, toxicology, hospital-acquired infections, sudden infant death and shaken baby syndromes); (iii) to assist human identification (skin, hair and body fluid microbiomes); (iv) for geolocation (soil microbiome or microbiome of bodies of water); and (v) to estimate postmortem interval (PMI) via thanatomicrobiome<ref>{{Citation |last1=Javan |first1=Gulnaz T. |title=Chapter 6 - What Is the "Thanatomicrobiome" and What Is Its Relevance to Forensic Investigations? |date=2018-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780128093603000060 |work=Forensic Ecogenomics |pages=133–143 |editor-last=Ralebitso-Senior |editor-first=T. Komang |access-date=2023-05-05 |publisher=Academic Press |language=en |isbn=978-0-12-809360-3 |last2=Finley |first2=Sheree J.}}</ref><ref>{{Cite journal |last1=Javan |first1=Gulnaz T. |last2=Finley |first2=Sheree J. |last3=Abidin |first3=Zain |last4=Mulle |first4=Jennifer G. |date=2016-02-24 |title=The Thanatomicrobiome: A Missing Piece of the Microbial Puzzle of Death |journal=Frontiers in Microbiology |volume=7 |pages=225 |doi=10.3389/fmicb.2016.00225 |issn=1664-302X |pmc=4764706 |pmid=26941736 |doi-access=free }}</ref> and epinecrotic<ref>{{Cite journal |last1=Pechal |first1=Jennifer L. |last2=Crippen |first2=Tawni L. |last3=Benbow |first3=M. Eric |last4=Tarone |first4=Aaron M. |last5=Dowd |first5=Scot |last6=Tomberlin |first6=Jeffery K. |date=2014-01-01 |title=The potential use of bacterial community succession in forensics as described by high throughput metagenomic sequencing |url=https://doi.org/10.1007/s00414-013-0872-1 |journal=International Journal of Legal Medicine |language=en |volume=128 |issue=1 |pages=193–205 |doi=10.1007/s00414-013-0872-1 |pmid=23749255 |s2cid=11357573 |issn=1437-1596}}</ref><ref name="Petkar">{{Cite web |last=Petkar |first=Tejaswini |date=2022-10-03 |title=Bacteria, Biofilms and forensic PMSI |url=https://micro-bites.org/2022/10/03/bacteria-biofilms-and-forensic-pmsi/ |access-date=2023-05-05 |language=en}}</ref> microbial community".<ref name="Microbial forensics: new breakthrou">{{cite journal |last1=Oliveira |first1=Manuela |last2=Amorim |first2=António |title=Microbial forensics: new breakthroughs and future prospects |journal=Applied Microbiology and Biotechnology |date=December 2018 |volume=102 |issue=24 |pages=10377–10391 |doi=10.1007/s00253-018-9414-6|pmid=30302518 |pmc=7080133 }}</ref> In fact, scientists estimate the time elapsed since death or the PMI by analyzing the stage of decay from bacterial decomposition<ref name="Petkar"/> or the bacterial succession patterns.

=== Bioterrorism and epidemiology ===
Bio terrorism occurs when biological components are used as warfare agents. Such biological weapons are microorganisms that  are deliberately dispersed to incapacitate or cause disease and death to humans, animals or plants. Biological warfare agents can be natural or genetically modified.<ref>{{Cite journal |last1=Roffey |first1=R. |last2=Lantorp |first2=K. |last3=Tegnell |first3=A. |last4=Elgh |first4=F. |date=2002-08-01 |title=Biological weapons and bioterrorism preparedness: importance of public-health awareness and international cooperation |journal=Clinical Microbiology and Infection |language=en |volume=8 |issue=8 |pages=522–528 |doi=10.1046/j.1469-0691.2002.00497.x |pmid=12197874 |issn=1198-743X|doi-access=free }}</ref> Nevertheless, these biological agents - be it viruses, bacteria or fungi are highly contagious.

Forensic microbiology also contributes to the development of epidemiology. By examining microorganisms obtained from infected individuals, scientists can determine a suspected source of infection, the type of infection present, and the evolution or mutation pattern of the microorganism. The application of a forensic microbiologist would be to examine the microorganisms isolated from infected individuals and compare it to known sources of infectious pathogens.<ref>{{Cite book |last1=Amorim |first1=Antonio |url=https://books.google.com/books?id=3XwqDwAAQBAJ&pg=PR5 |title=Handbook Of Forensic Genetics: Biodiversity And Heredity In Civil And Criminal Investigation |last2=Budowle |first2=Bruce |date=2016-08-30 |publisher=World Scientific |isbn=978-1-78634-079-5 |language=en}}</ref>

"It is important to remember that biological agents that can be used as weapons are often found in the environment. For this reason, it is always difficult to determine whether infections associated with these bioagents are accidental or purposely started".<ref name="Microbial forensics: new breakthrou" /> While not the first, or only, incidence of bioterrorism, perhaps the most notable case in recent memory involved the sending of at least four anthrax-containing envelopes in the United States in September and October 2001. "At least 22 victims contracted anthrax due to the mailings: 11 individuals contracted inhalation anthrax, with 5 of these infections resulting in fatalities; another 11 individuals suffered cutaneous anthrax. In addition, 31 persons tested positive for exposure to B. anthracis spores".<ref>{{cite journal |last1=Rasko |first1=D. A. |last2=Worsham |first2=P. L. |last3=Abshire |first3=T. G. |last4=Stanley |first4=S. T. |last5=Bannan |first5=J. D. |last6=Wilson |first6=M. R. |last7=Langham |first7=R. J. |last8=Decker |first8=R. S. |last9=Jiang |first9=L. |last10=Read |first10=T. D. |last11=Phillippy |first11=A. M. |last12=Salzberg |first12=S. L. |last13=Pop |first13=M. |last14=Van Ert |first14=M. N. |last15=Kenefic |first15=L. J. |last16=Keim |first16=P. S. |last17=Fraser-Liggett |first17=C. M. |last18=Ravel |first18=J. |title=Bacillus anthracis comparative genome analysis in support of the Amerithrax investigation |journal=Proceedings of the National Academy of Sciences |date=2011-03-22 |volume=108 |issue=12 |pages=5027–5032 |doi=10.1073/pnas.1016657108|pmid=21383169 |pmc=3064363 |bibcode=2011PNAS..108.5027R |doi-access=free }}</ref> However, the advancements in PCR and whole-genome sequencing allowed scientists to collaborate with the FBI and identify the source of the letter spores.

==== Differentiating a biowarfare attack from a normal epidemiology outbreak ====
The basic epidemiologic approach to evaluating a potential bioterrorist or biowarfare attack differs from any standard epidemiologic investigation. The first step uses laboratory and clinical findings to confirm that a disease outbreak has occurred. Once the case definition and attack rate have been determined, the outbreak can be characterized in the conventional context of time, place, and person. These data provide crucial information in determining the potential source of the outbreak. An epidemic curve can be calculated using data gathered on cases over time. The disease pattern is important to differentiate between a natural outbreak and an intentional attack. A bioterrorism attack is most likely caused by a point source, with everyone coming in contact with the agent at approximately the same time. Additional characteristics investigated in determining whether it is the result of a biological attack are: the presence of a large epidemic; more severe disease than expected for a given pathogen; a disease that is unusual for a given geographic area; and multiple simultaneous epidemics of different diseases.<ref>{{Cite web |title=Epidemiology of Bioterrorism {{!}} Office of Justice Programs |url=https://www.ojp.gov/ncjrs/virtual-library/abstracts/epidemiology-bioterrorism |access-date=2023-05-31 |website=www.ojp.gov}}</ref>

=== Postmortem analysis ===
"Post-mortem microbiology (PMM) aims to detect unexpected infections causing sudden deaths; confirm clinically suspected but unproven infection; evaluate the efficacy of antimicrobial therapy; identify emergent pathogens; and recognize medical errors. Additionally, the analysis of the thanatomicrobiome may help to estimate the post-mortem interval.".<ref>{{cite journal |last1=Fernández-Rodríguez |first1=A. |last2=Burton |first2=J.L. |last3=Andreoletti |first3=L. |last4=Alberola |first4=J. |last5=Fornes |first5=P. |last6=Merino |first6=I. |last7=Martínez |first7=M.J. |last8=Castillo |first8=P. |last9=Sampaio-Maia |first9=B. |last10=Caldas |first10=I.M. |last11=Saegeman |first11=V. |last12=Cohen |first12=M.C. |title=Post-mortem microbiology in sudden death: sampling protocols proposed in different clinical settings |journal=Clinical Microbiology and Infection |date=May 2019 |volume=25 |issue=5 |pages=570–579 |doi=10.1016/j.cmi.2018.08.009|pmid=30145399 |doi-access=free }}</ref> There is currently an extensive amount of research being performed, most notably using the famous "body farms" throughout the United States, to determine if there is a consistent microbial decomposition "clock" that could be used by itself, or in conjunction with other techniques (such as forensic entomology) to help estimate postmortem intervals. One such group has made extensive headway into describing such a microbial clock, and "believes she's within two to five years of testing her clock in a real crime scene scenario".<ref name="ReferenceC">{{cite journal |last1=Beans |first1=Carolyn |title=News Feature: Can microbes keep time for forensic investigators? |journal=Proceedings of the National Academy of Sciences |date=2018-01-02 |volume=115 |issue=1 |pages=3–6 |doi=10.1073/pnas.1718156114|pmid=29295964 |pmc=5776831 |doi-access=free }}</ref> However, if a reliable and consistent microbial clock is determined to exist, "it's too soon to know whether the microbial clock will pass scientific and legal muster," (Beans) and "a judge would also have to determine that the microbial clock meets the standard for admission of expert testimony".<ref name="ReferenceC"/>

=== Water sample analysis ===
In cases involving a body of water at or near the scene of a crime, a sample of the water can be extracted and analyzed under a light microscope for microorganisms. One such microorganism that are analyzed within samples of fresh water are diatoms, microscopic algae of varying shapes. Different bodies of water have been found to contain unique sets of diatoms and therefore, a piece of evidence found in a specific body of water will contain unique diatoms on it found only in that specific body of water. Therefore, the diatoms on a questioned object or body can be compared to the diatoms from a body of water to determine whether it had been present in the water.<ref>{{Cite web |title=What are diatoms and what can they tell us about water quality? |url=https://www.apemltd.com/what-are-diatoms-and-what-can-they-tell-us-about-water-quality/ |access-date=2023-05-06 |website=APEM |language=en}}</ref>

== Current issues ==
{{Globalize|section|US|date=August 2021}}

=== Sexual assault kit backlog ===
Prior to DNA testing, many sexual assault cases could only rely on "he said, she said" and possible witnesses. Even once DNA analysis was available, many sexual assault kits, or SAKs, were never tested and thrown into a backroom or storage facility, only to be forgotten until discovered. Since DNA analysis is frequently utilized in most cases, most SAKs are examined and analyzed. However, the issue remains about the preexisting SAKs that have never been tested. A prevalent issue then, that still extends to now, is the absence of funds to process and analyze these SAKs. Many districts would dedicate their funds to homicides or more high-profile cases and sexual assaults would be swept aside. The biggest concern about all of these SAKs, is how to go about processing all of them, especially as more and more are being found each year.<ref>{{Cite web|url=https://permanent.access.gpo.gov/gpo67935/249234.pdf|title=Creating a Plan to Test a Large Number of Sexual Assault Kits|last=National Institute of Justice|date=March 2016}}</ref>

=== Cold cases ===
With the considerable advances in DNA analysis, old, open cases with intact evidence can be examined for biological evidence.<ref name=":2" /> New profiles are uploaded to [[Combined DNA Index System|CODIS]] every day so the base population to search and compare to increases. Biological testing for cold cases, specifically homicides, encounters similar roadblocks as the SAKs - lack of funds or the DNA samples have not been properly stored; thus too much degradation has occurred for viable analyses.

==Popular culture==

In popular culture, forensic biology is frequently portrayed in shows like ''[[Law & Order]]'', [[Hannibal (TV series)|''Hannibal,'']] ''[[Bones (TV series)|Bones]]'', ''[[CSI (franchise)|CSI]]'', ''[[Dexter (TV series)|Dexter]]'' and ''[[Castle (TV series)|Castle]]''. However thanks to Hollywood's depiction of forensic science, the analysis of biological evidence has fallen prey to the [[CSI effect|CSI Effect]], which results in the public's perception of its capabilities being severely distorted and its limits blurred.

==See also==
* [[DNA profiling]]
* [[Forensic chemistry]] 
* [[Forensic science]]

==References==
{{reflist|30em|refs=Avon, Sylvie Louise. "Forensic Odontology: The Roles and Responsibilities of the Dentist." Journal of the Canadian Dental Association, vol. 70, no. 7, 2004, p. 6.}}

[[Category:Branches of biology]]
[[Category:Forensic disciplines|Biology]]