Many people ask me about forensic DNA testing.
They want to do paternity testing, relationship testing, or just confirm their family tree. But a critical test subject is either deceased or otherwise unavailable to submit a DNA sample.
This is where the principles of genetic testing can sometimes help you get DNA indirectly.
Read on to learn more about the various options for getting a valid DNA sample.
Human DNA Sources
Today, most DNA testing laboratories collect DNA from willing subjects through cheek cells, saliva, or sometimes blood. A small number of laboratories will also extract DNA from alternative sources of DNA.
The following list shows some of the possibilities:
- Hair
- Teeth
- Dentures
- Toothbrush
- Dental Floss
- Razors and Electric Razor Clippings
- Fingernail or Toenail Clippings
- Hearing Aid
- Ear Wax
- Used Kleenex
- Gum
- Cigarette Butts
- Clothing Stained with Blood or Sweat
- Licked Envelopes and Stamps
- Semen
- Urine
DNA Collection
There are many hurdles to overcome in DNA sample collection. For example, hair only has DNA in the roots. So cut hair and hair that just fell out won’t work. And one hair isn’t enough. You need quite a few hairs.
If you touch an object with the subject’s DNA on it, you can contaminate it with your own DNA, rendering it useless. Also, samples should generally be stored in dry paper envelopes rather than plastic bags.
Watching CSI does not make you a trained forensic specialist. That’s why I recommend you talk to your test lab BEFORE you attempt to collect DNA samples. Decide what samples to go for and get specific tips for safe collection, storage, and shipping.
Also, be sure to ask about the lab’s success rate at extracting DNA from the types of samples you are considering. One lab told me, for example, that the likelihood of collecting DNA from licked envelopes and stamps is only about 10%. Keep in mind that any lab will charge you for ATTEMPTING to extract DNA. You pay the fee whether they find any useful DNA or not.
DNA After Death
It is sometimes possible to get DNA after the subject has died. If death was recent, there may be blood or tissue samples at the hospital or funeral home. For example, the hospital may have taken a biopsy specimen in a medical procedure before death.
If the subject has already been buried, the body could be exhumed to obtain a sample. Obviously, this is a drastic (and expensive) step that requires legal permission in most areas. The chance of recovering useful DNA is fairly good. On the other hand, the chance of recovering DNA from cremated remains is essentially zero.
For more information on forensic DNA testing see this blog post by Roberta Estes.
Legal Issues in Forensic DNA Testing
I don’t give legal advice. But collecting another person’s DNA without their permission may be illegal in some areas. In any case, the DNA results obtained through these alternative samples would be for personal information only. Forensic DNA testing cannot provide a legal paternity test. That’s because you cannot prove that you collected the right person’s DNA.
One exception might be the DNA after death situation. A tissue sample collected from the subject for a medical procedure and transferred by the hospital directly to the DNA testing lab MIGHT satisfy the chain of custody requirements for a legal test.
