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Frequently Asked Questions - Forensic Biology

DNA analysis will not be performed on brief contact items. Brief contact items are those items considered unlikely to contain sufficient transfer of 

skin cells to the object. Examples of brief contact items would include door handles, counter tops, etc. Touch DNA analysis can be performed on 

items that would result in skin cells being left on objects due to extended contact. Examples of Touch DNA extended contact items would include 

some clothing, cigarette butts, straws, bottles, cans, etc.

1. The evidence submitted has to be from a crime scene
2. The evidence cannot be seized from the suspect’s person or his possession
3. The profiles developed are not from the victim(s)

Please remember evidence can be informative for your case without being CODIS eligible; for example, victim blood on suspect pants.  

For additional guidance or to discuss a specific case, please contact the CODIS Unit.

Offender samples used by the DNA Databank do not have an associated chain of custody and are generally inadmissible in court.  A new sample is needed to do a direct comparison between the individual listed in the CODIS hit letter and your case.  No statistical analysis can be performed without a known DNA sample.

No, the offender collection kits are for the DNA Databank only. They do not have a chain of custody associated with them, and are not considered

evidence. You do not need a special kit to collect a known DNA sample. Using sterile swabs and storing them in a sealed evidence envelope is


No, offender DNA samples/profiles are confidential and cannot be released for use in a civil case. Other samples to consider: paternal grandparents,

paternal (full) siblings, medical samples such as biopsy slides, or teeth.

The Federal Bureau of Investigation facilitates the use of a national DNA database, which is called the Combined DNA Index System (CODIS) 

 database.  It can be used to search profiles within the state of Oklahoma and throughout the United States.  CODIS is a useful tool in providing 

  investigative leads to law enforcement agencies throughout the state. It is particularly useful when there are no suspects or a suspect has not yet 

  been developed. CODIS is also providing useful information on cold cases. 

Yes, if there is no suspect and there is evidence from the crime scene, a DNA profile can be obtained and entered into the Combined DNA Index System (CODIS) database to attempt to develop an investigative lead. If there is a CODIS hit to an unknown suspect, then a hit letter will be sent to the investigator. At that time a known buccal swab should be obtained from the individual and submitted to the laboratory. Comparisons will then be made between the known reference sample and the evidence submitted. 

In most cases, the amount of sample that is required for DNA analysis is minimal, and every effort is made to keep at least half of the stain for additional testing if necessary.  If a sample will be consumed in testing, the laboratory will contact the assigned officer or District Attorney’s office to obtain written permission to consume the sample.

Every case is different. An analysis is dependent on the number of samples that were submitted and the current backlog of the laboratory at the time. The duty biologist or supervisor of the laboratory analyzing the evidence may be contacted to get an estimate of the turn-around time. Estimates should not be mistaken for guaranteed time frames.

A known reference sample is a DNA sample obtained from a particular individual (i.e. buccal swab from a victim or suspect). Known reference samples should be collected as buccal swabs. A buccal swab is a swabbing of the inside of a person’s cheek and gum area. A sterile swab should be used when taking a known reference sample. A minimum of two swabs should be used, and these swabs should be taken at the same time. The swabs should be allowed to air dry in a swab box or another appropriate container. The packaging should be clearly labeled with the individual's name. The buccal swabs do not need to be refrigerated. Known reference samples from the medical examiner’s office are typically submitted on a blood card.

Samples should be collected in a way that will avoid sample destruction and degradation.  Biological evidence is best preserved in a dry, cooler

environment.  Items of evidence should be packaged in brown paper sacks, evidence envelopes, or similar packaging material.  Biological

evidence should never be packaged in plastic bags.  Specific packaging information can be found in the Evidence Collection Manual.

Biological evidence must be retained in accordance with Title 22 S 1372-A.  "A criminal justice agency having...custody of biological evidence from a violent felony offense...shall retain and preserve that biological evidence for such a period of time as any individual convicted of that crime remains incarcerated."