Trace DNA – also commonly referred to as touch or contact DNA, is widely believed to be the DNA from skin cells left behind when someone touches an object or individual. However, studies have shown DNA can also be left on an object in a variety of unintentional ways including coughing, sneezing, or even talking near an object. Likewise, the absence of DNA on an object is not evidence that it was not handled or possessed. As a result, DNA testing is not appropriate for certain types of evidence.
Buccal Swabs – (Pronounced “buckle”) swab(s) collected from the inner cheek of the mouth to use as a known DNA sample. Any swabs collected other than from the inner cheek are not buccal swabs. Do not use convicted offender and arrestee kits for casework submissions. DNA profiles from offender and arrestee submissions cannot be used for casework comparisons.
Combined DNA Index System (CODIS) – A national database operated by the Federal Bureau of Investigation (FBI) that stores the DNA profiles of missing persons, individuals convicted of crimes and forensic samples collected from crime scenes. For a DNA profile to be entered it must have originated from the scene of the crime and must be attributable to a perpetrator. No names or identification information is stored in CODIS, and DNA profiles cannot be referenced for comparison. However, since new DNA profiles are constantly being entered, the database is searched daily for new matches.
Deoxyribonucleic Acid (DNA) – The genetic material found in various body tissues (muscle, fetal tissue, skin, etc.) and body fluids (semen, blood, saliva, etc.). Because an individual’s DNA is the same throughout the body and different from individual-to-individual, it can be used to determine whether a biological substance may have been deposited by a specific individual.
STR DNA Analysis – STR DNA analysis is the most widely used method in crime laboratories and the results are unique to every individual (except for identical siblings). STR (Short Tandem Repeat) testing targets and copies specific locations in the DNA molecule. This testing can be performed to identify not only the gender of the biological material source but also generate a genetic profile which provides the ability to distinguish between two individuals with a considerable degree of confidence.
Y-STR DNA – Male specific DNA found in the nucleus of most cells of the body. Y-STR analysis is used to copy locations on the Y chromosome and Y-STR data can only be obtained from male individuals. This type of DNA is inherited paternally. This type of testing may be useful when samples are mixtures of male and female DNA or when there is very little DNA from a male contributor. Y-STR testing has its limitations since close male relatives will have the same Y-STR profile.