DNA identification: basics
- Method
The DNA profile of a body is compared with that of personal items or of relatives to confirm who it is.
What it is
DNA identifies because much of the genetic information is unique to each person (except identical twins). Forensic identification relies mainly on STRs, short tandem repeats in nuclear DNA whose number of repeats varies widely between people. When DNA is badly degraded (old bones, hairs without roots), mitochondrial DNA is used: it is present in many copies per cell and is inherited only through the maternal line; the Y chromosome follows the paternal line. The body's profile is compared with a sample from the person (toothbrush, stored medical sample) or with biological relatives (kinship analysis). It is the only primary method that needs no prior records of the person.
Accuracy and limits
- An exclusion is definitive; a match is expressed with its statistical weight.
- Parent-child kinship is confirmed well by STRs; telling full siblings from half-siblings is harder.
- Mitochondrial DNA cannot distinguish between relatives on the same maternal line.
- Contamination with DNA from whoever handles the sample is a real risk.
What it is based on
- Each person inherits one allele of each STR from the father and one from the mother: this allows kinship analysis.
- Mitochondrial DNA is the same in siblings and in all relatives on the maternal line.
- Identical twins share the same STR profile.
- The result is expressed as a statistical measure of the strength of the match, not as absolute certainty.
How it is applied
- Choose the body sample according to its state: blood or muscle if fresh; dense bone or a tooth if degraded.
- Obtain reference samples: personal-use items or cheek swabs from biological relatives, with consent.
- Prefer parents and children as references; if they are missing, several siblings or other relatives.
- Package without contamination (gloves, mask, separate containers) and send under chain of custody.
- The laboratory compares profiles and calculates the probability of kinship or of a match.
Next step: what to do and document
- Wear gloves and a mask when taking DNA samples and do not touch them with bare hands.
- In decomposed or burnt bodies, ask the laboratory which sample is most useful (for example, a tooth or a piece of long bone).
- Record whose each reference sample is, the stated relationship and the signed consent.
- For enforced disappearances, Law 1408 of 2010 (art. 5) provides that relatives authorise, with informed consent, the entry of their samples into the Missing Persons Genetic Profile Bank.
- Official text checked on 2026-11-05 at funcionpublica.gov.co.
Common mistakes
- Taking the reference from a relative by marriage (no biological link).
- Storing wet samples in plastic, where they degrade.
- Treating a mitochondrial DNA match as an individual identification.
- Forgetting that identical twins have the same profile.
Test yourself
Think of the answer, then tap the question to see it.
Which DNA markers form the basis of forensic identification profiles?
STRs (short tandem repeats) of nuclear DNA, which vary widely between people.
When is mitochondrial DNA useful, and what is its limit?
In degraded samples, because of its many copies per cell; its limit is that it is inherited maternally and is identical in relatives on that line.
Which relatives are the best references for identifying a person by DNA?
First-degree ones: biological parents and children; if they are missing, several siblings or other relatives.
Elsewhere in DurgiPedia
Connections
Educational content on forensic and legal medicine; not legal advice and no substitute for the technical guides of Colombia's National Institute of Legal Medicine and Forensic Sciences. Laws change: each page links the official text and says when it was last checked. For a real case, follow the guide in force and ask the competent authority.
Sources: Disaster Victim Identification Guide, Annexure 8: Methods of identification (INTERPOL, 2023); Recent advances in forensic biology and forensic DNA typing: INTERPOL review 2019–2022 (Forensic Science International: Synergy, 2023); Ley 1408 de 2010, tribute to victims of enforced disappearance and measures for their location and identification (Función Pública, Gestor Normativo, 2010).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.