A Quick Guide for Obtaining the DNA Sample

DNA Exemplars and Law Enforcement

By: Joseph L. Giacalone

3 Ways Obtain DNABy now you have seen all of the television shows, read the mystery books and listened to newscasts on how DNA help solve a cold case. DNA happens to be one of the most important law enforcement tools used to solve crimes. However, there is one constant in all of this and that is how law enforcement can lawfully obtain a DNA exemplar.

Law enforcement agencies have been playing the forensic “catch-up” game for a number of years. They learn the new methods and technologies and then the forensic science community discovers a new way of doing it. It is a constant learning curve for law enforcement.  The advances in forensics and DNA are exponential and law enforcement has made a herculean effort to stay on top of this technology.

Obtaining a DNA exemplar is just like collecting other pieces of evidence. Law enforcement understands that the public now demands to see the forensic evidence, especially DNA, that ties the suspect to the victim, the suspect to the scene or the suspect to the weapon. Call it the “CSI Effect” or anything else that you want to, but the jury wants to see more of it. Many times investigators recover DNA at a crime scene, but when the sample is entered into the Combined DNA Index System (CODIS), it comes back as “No Hit.” As the investigation progresses and suspects are developed, investigators need to obtain exemplars to either exclude or include the suspect.

Each action that investigators take could have a reaction in the suspect. Move too soon and you can spook them, move to late and the hunt is on. The question remains, “How can law enforcement legally obtain a DNA exemplar from a suspect? There are only three (3) ways to do so that I refer to as the 3 Cs:

    1. Consent
    2. Court Order
    3. Covertly


In order to get consent, you have to ask. The suspect must agree to provide the sample voluntarily, knowingly and intelligently. Which means that he is old enough, understands what he/she is doing and the consequences of the action and they weren’t tricked, forced or coerced. But what do you think will happen once the investigator asks for a DNA sample? Right, your suspect is gone in the wind and your investigation just got ten times more difficult.

Court Order

In order to get a warrant for taking a DNA sample, investigators must have probable cause. Generally, in these cases, the suspect is already in custody, so there is no threat of him fleeing and probable cause has already been established. If he wasn’t in custody, that would mean that probable cause has not been established and therefore couldn’t get a warrant.


Obtaining a DNA sample covertly, (secretly or surreptitiously) is not as easy as it sounds or shown on television. Detectives must work carefully and fast when they need to recover a discarded sample. On television, detectives are always able to recover the bottle of water or can of soda for their exemplar. However, the target probably watches television too! Now investigators have to conduct surveillance and wait for the suspect to spit, discard a cigarette or half eaten food to obtain the sample.

Law enforcement must carefully obtain a DNA exemplar or risk it being excluded in pretrial evidence hearings. Sometimes obtaining a DNA exemplar is the only thing standing in the way of an arrest and conviction and even exoneration of innocent person wrongfully accused.