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How to conduct a DNA test with a deceased person?

Updated: Mar 26


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To perform a DNA test, the choice of the sample used is crucial. It is generally recommended to send buccal swabs with a saliva sample to the laboratory for kinship analysis. However, it is also possible and common to use non-standard samples, including nail clippings, blood samples, ear swabs (earwax), or other similar samples. These can all be collected quite easily and can also be used where buccal swabs are not possible.


Nevertheless, there are situations where a DNA test may be considered after a person's funeral. In this case, DNA samples can also be collected under certain conditions to obtain the most reliable result.


How to retrieve samples that belonged to the person?


It is always easier initially to search for samples that belonged to the deceased person. The type of sample you can use will greatly depend on its preservation and, of course, the time that has elapsed between the collection from the person and the start of the analyses. In the majority of cases, if the deceased has been dead for several years, the samples will provide only a degraded and incomplete genetic profile for DNA analysis. Please find below a non-exhaustive list of samples that can be used in this situation:


  • Hair sample with the root

  • Nail clippings

  • Blood stain on clothing or bandage

  • Earwax on cotton swabs

  • Teeth

  • Razor

  • Toothbrush


It is important to note that post-mortem genetic tests usually cost more to conduct due to the limited number of available samples and their condition during genetic analysis. It is very common for DNA extraction to require multiple attempts before obtaining a complete genetic profile.


It is thus recommended to send as many samples as possible to the laboratory.

Do not forget the family's consent.


Consent for the use of a deceased person's sample can only be provided by the closest relatives unless there is a written statement from the person before their death. The laboratory verifies the legal kinship and the death certificate of the participant.


In forensic cases, a court order is necessary to obtain a sample without the approval of the closest relative or the deceased's permission, for example, in a homicide case where a DNA test needs to be performed for clarification.



Which samples to collect from a deceased body?



It goes without saying, but the less time the body is left to decompose, the more chances there are of obtaining viable samples. Some samples are viable only for a short period before they become too degraded to be used.


Nails and Hair:

Nails and hair follicles with the root can be recovered from the deceased body without visible degradation. They can be preserved for several months before analysis and represent the easiest to extract.


Bones and Teeth:

Bones are high-quality samples for preserving DNA. In general, the larger the chosen bone, the more bone marrow it will provide, containing the person's genetic information. Teeth, like bones, are excellent samples, remaining attached to the jaw, preserving the DNA present in the root for a very long period. Their particularity is that they can be easily removed.


Blood:

Some funeral homes collect and preserve a blood sample available for one or two years. This can be done upon request or as part of the service provided by the funeral home. Like other samples, the longer the blood is left to dry, the less reliable it is to test.


The collection of control samples before burial is an option that can only be done during a very short period before the embalming process begins. Otherwise, the embalming fluid will interfere with the DNA sample.

Exhumation for DNA Testing


Exhumation involves removing a coffin or the remains of the deceased from a grave or vault. It requires authorization, which can be requested by the family of the deceased or initiated by the municipality, social security, or the judiciary.


Exhumation of a body for DNA samples is interesting because there is a chance that preserved genetic information may still be available on the person. However, this process is not always straightforward, as it must take into account family consent, religious prohibitions, and the country's laws on post-mortem parentage.


The exhumation process can be a lengthy, complicated, and very costly procedure. The actual condition of the body and the state it might be in when unearthed must also be considered. The older the death, the less likely you are to find valid samples for testing.


Can DNA testing be done with cremated ashes?


Another type of sample that can be tested in a genetic analysis comes in the form of cremated ashes. Ashes result from cremation, a funeral technique aimed at reducing the deceased's body to ashes through heat. Cremation is a wish that must be explicitly expressed during the person's lifetime.


Unfortunately, testing DNA from incinerated remains has very little chance of providing accurate results. When a body is burned, the temperatures used carbonize the remains to a point where the samples are not reliable for use, as the heat destroys the DNA necessary for analysis.


It is possible that a small part of the body is viable for the test, such as a piece of bone, but only when cremation is incomplete. The laboratory can still attempt to test this as a sample, but given that it has been exposed to the same high heat, it is more likely than not that the samples will not be viable.


Please keep in mind that the ashes sent for testing will be used for analysis and cannot be returned to the family. This is important to consider because the test cannot be repeated, and you will no longer have the ashes of the deceased.


For the quantity of samples, the laboratory requests:


  • For an adult male: 2500-3000 g

  • For an adult female: 1800-2000 g


Usually, incinerated remains pass into the possession of the closest relative, just like with a body, so they can easily access a sample for testing. Otherwise, a court order is required to gain access. Of course, legal consent must always be provided by the family to request an analysis from an accredited laboratory.


The DNA family reconstruction test


If the provided samples from the deceased yield no results or if there is no available sample, the last option is to conduct a DNA test with all the closest family members.


A portion of our DNA is shared with our family, and the closer they are to us, the higher the percentage of shared DNA. Therefore, for the genetic search of a person who is not present, it may be worthwhile to include the genetically closest individuals. This can include:


Grandparents (grandmother & grandfather)

Parents (father & mother)

Aunts & uncles

Siblings (brothers & sisters)

Nieces & nephews

Grandchildren (grandson & granddaughter)

The best tests are those related to direct parents, and the reliability depends on the number of participants available for the search for parentage. For example, in a paternity search, DNA tests of grandparents, avuncular tests, and tests of siblings are the best options to gather the father's profile.


These types of tests do not require any legal or administrative procedures if all participants agree to provide their DNA in the search for the deceased.


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