According to the National Crime Information Center (NCIC), there were a total of 627, 911 missing person records in 2013. By the end of the year, 84, 136 of these cases were still unsolved (active).
Statistics also indicate that in 2013, there were 5,000 reported unidentified persons in the United States. A century ago most of these cases would have gone unsolved.
However, modern advances in the fields of science and technology make it more possible for solve missing or unidentified person cases. Today, law enforcement agencies use DNA testing to identify individuals or even as forensic evidence in tracking down missing persons..solve missing or unidentified person cases. Today, law enforcement agencies use DNA testing to identify individuals or even as forensic evidence in tracking down missing persons.
Types Of DNA Tests Used To Obtain Forensic Evidence
i. Short Tandem Repeats (STRs)
STRs are present in genomes – the complete set of genetic material in a cell or organism. Analysis of 15 or more of these STRs located in the non-sex chromosomes is used to ascertain family relationships with greater precision and accuracy.
STR analyses are not always successful, particularly after the degradation of human remains. However, it is possible to use mini-STRs with more success when dealing with degraded DNA.
ii. Mitochondrial DNA
Mitochondrial DNA testing uses DNA contained in the mitochondria. It is inherited from the mother alone. This testing makes it possible for experts to match remains of unidentified persons with their maternal grandmothers, aunts or uncles as well as with siblings.
iii. Sex Chromosome DNA Tests
These are used to make connections between unidentified persons and relatives from the paternal line of the family. Experts use STRs located on the Y chromosome. However, just like mitochondrial DNA profiling, this kind of test is not very accurate because the Y chromosome is not unique.
iv. Single Nucleotide Polymorphisms (SNPs)
DNA tests that use SNPs are useful in situations when there is a severe degradation of forensic evidence.
Standard Process Of DNA Analysis
There are five standard steps involved in a conventional DNA analysis process. These include;
i. Retrieval which involves the collection of forensic evidence, storage of remains and extraction of DNA from human remains or the forensic evidence collected.
ii. Secondly, the DNA is quantified.
iii. The production of multiple copies of the DNA fulfills the purpose of characterizing it. This step is known as amplification of DNA.
iv. Once the DNA is amplified, it is separated to allow for identification.
v. DNA samples are compared with known DNA profiles in a qualitative and quantitative manner. This was the purpose behind the establishment of the National DNA Index System in 1998.
NDIS is part of a larger database known as the Combined DNA Index System (CODIS) used by all the different law enforcement agencies in the United States.
Experts can use DNA profiles such as those from convicted offenders, unknown individuals from other forensic evidence, missing persons, biological relatives of the disappeared (contributed voluntarily) and remains of unidentified persons.
The information from the analysis is then used to solve missing person or unidentified person cases.
vi. Finally, the analysis of the final report brings out the technical accuracy.
Interpretation Of Results
DNA testing can yield three types of results. Inclusion is when the DNA profile of a suspect or an unidentified person is consistent with forensic evidence from the crime scene or with known relatives.
Exclusion is when the DNA profile is not consistent with DNA from crime scene evidence or the purported relative. Lastly, DNA testing could yield inconclusive results due to some reasons including when the DNA sample is mixed.
Advantages Of Using DNA As Evidence
Using DNA testing to identify missing persons or solve active missing person cases has several benefits to it;
i. Firstly, experts can test any DNA-containing biological trace evidence. This is because the composition of DNA is the same in all the cells of the body. It is, therefore, possible to test evidence such as hair, semen, skin, bone marrow, blood, teeth or even saliva among other biological materials.
ii. Secondly, DNA testing is made effective by the fact that everyone is genetically different except for identical twins. This makes it more precise than tests such as blood typing. It also makes it possible for law enforcement to link crime scenes with specific suspects.
iii. DNA tests do not require a huge amount of biological material for them to work. A single strand of hair or blood stain is enough as forensic evidence.
iv. DNA degrades particularly slowly in hard tissues such as bones or teeth. This means that in cases where the only available specimens are old or degraded, it is still possible to use DNA testing to identify a missing person. This is a significant benefit especially in situations such as war or catastrophes.