What can be tested for traces of DNA?
DNA Samples: What Can Be Tested for DNA?
One of the most common questions people ask before ordering a DNA test is:
"What type of sample can I submit?"
The answer depends on the type of testing being performed and whether the person being tested is available to provide a standard DNA sample.
For most DNA tests, a simple cheek swab provides the best and most reliable source of DNA. However, in situations where a swab sample cannot be obtained, many other biological materials may also be suitable for testing.
This guide explains the most common DNA sample types, their advantages, and the factors that can affect testing success.
Quick Answer: What Can Be Tested for DNA?
The most reliable DNA sample is a cheek swab collected directly from the individual being tested.
When a cheek swab is unavailable, laboratories may also be able to test:
hair with roots
blood stains
saliva stains
toothbrushes
fingernail clippings
underwear stains
tissues
teeth
other biological materials
The success of testing depends on the quantity and quality of DNA present in the sample.
In This Article
Standard DNA samples
Forensic DNA samples
What makes a good DNA sample
Common sample types used for testing
Risks of forensic samples
Frequently asked questions
Standard DNA Samples
For most relationship DNA tests, the preferred collection method is a buccal swab.
A buccal swab resembles a cotton swab and is gently rubbed against the inside of the cheek to collect cells containing DNA.
Benefits of cheek swabs include:
painless collection
high DNA quality
fast laboratory processing
reliable results
Because of these advantages, buccal swabs remain the recommended sample type for:
paternity tests
sibling tests
grandparent tests
avuncular tests
twin zygosity tests
Y-STR tests
What Are Forensic DNA Samples?
Also called Non-Standard Samples (NSS) forensic DNA samples are used when a standard cheek swab cannot be obtained.
This may occur when the individual is:
unavailable
unwilling to participate
missing
deceased
Unlike cheek swabs, forensic samples are collected from personal items or biological evidence.
These samples often require additional laboratory processing and may carry a higher risk of DNA degradation.
Common Types of Forensic DNA Samples
Hair with Roots
Hair samples can often be tested when the root remains attached.
Generally:
6-8 hairs are recommended
hair with the root attached provide the best results
cut hair usually does not contain sufficient DNA
Because nuclear DNA is located within the root, hairs without roots are less likely to produce usable results.
Blood Stains
Dried blood stains are often excellent DNA sources.
Examples include:
bandages
tissues
cotton
paper
clothing
Properly preserved blood stains may retain usable DNA for years.
Saliva Stains
Saliva can often be recovered from:
cigarette butts
drinking containers
tissues
envelopes
stamps
clothing
Because saliva contains cells from the mouth, it may provide a useful DNA source.
Toothbrushes
Toothbrushes frequently contain saliva and oral cells.
They are among the most commonly submitted forensic DNA samples for relationship testing.
Fingernail Clippings
Fingernail clippings may contain DNA but generally have lower success rates than many other sample types.
Providing multiple clippings may improve the chances of obtaining usable DNA.
Underwear and Biological Stains
Items containing dried biological stains may sometimes be suitable for DNA testing.
Examples include:
underwear
tissues
sanitary products
diapers
The success of testing depends on the amount and condition of the biological material present.
Teeth
Teeth are often used in more challenging forensic cases.
Molars, premolars, and canine teeth typically provide the best opportunity for DNA recovery.
Additional costs and laboratory processing is required and teeth are not considered normal NSS or forensic samples. Please contact us before submitting teeth as a sample.
Can Clothing Be Tested for DNA?
Yes.
Clothing may contain biological material such as:
saliva
blood
semen
skin cells
The success of DNA testing depends on:
how much biological material is present
how the item was stored
whether the item has been washed
Learn more: How DNA Gets on Clothing
What Makes a Good DNA Sample?
Several factors influence testing success.
The best DNA samples typically:
contain visible biological material
have been stored properly
remain dry
have minimal environmental exposure
Samples may become more difficult to test when exposed to:
heat
moisture
sunlight
mold
excessive handling
Are There Risks to Using Forensic Samples?
Yes.
Unlike cheek swabs, the quality of DNA in forensic samples cannot be guaranteed.
Potential challenges include:
degraded DNA
contamination
insufficient biological material
multiple DNA contributors
In some cases, even advanced laboratory testing may be unable to recover usable DNA.
Learn more: What Happens if No DNA is Found?
Frequently Asked Questions About DNA Samples
What Is the Best DNA Sample for Testing?
A cheek swab collected directly from the tested individual is generally considered the best sample type.
Can Old Samples Still Be Tested?
In many cases, yes.
The success of testing depends on the sample type and storage conditions.
Can Hair Be Used for DNA Testing?
Yes, provided the hair contains an intact root.
Cut hair generally does not contain sufficient nuclear DNA for most tests.
Can Clothing Be Tested for DNA?
Yes.
Biological material present on clothing may sometimes provide a suitable DNA source.
What Happens If a Sample Does Not Contain Enough DNA?
If insufficient DNA is recovered, the laboratory may be unable to develop a usable DNA profile.
Choosing the Right DNA Sample
The quality of the DNA sample is one of the most important factors in successful testing. While cheek swabs remain the preferred option, many forensic samples may also provide useful DNA when properly collected and preserved.
Understanding which sample types are most suitable can help maximize the chances of obtaining reliable and meaningful results.
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https://validitygenetics.com/news/how-long-do-dna-samples-last
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https://validitygenetics.com/news/how-dna-gets-on-clothing
What Happens if No DNA is Found?
https://validitygenetics.com/news/what-happens-if-no-dna-is-found
Can I use Discreet DNA Samples for Relationship Testing?
https://validitygenetics.com/news/can-you-use-discreet-dna-samples-for-relationship-testing
Cited References:
National Institute of Justice. DNA Evidence Basics
https://nij.ojp.gov/topics/articles/dna-evidence-basicsNational Human Genome Research Institute. DNA and Genetic Testing
https://www.genome.govAmerican Academy of Forensic Sciences (AAFS)
https://www.aafs.org
