Some DNA testing looks at one sample and can tell something useful about it. Other types of tests compare two or more samples, to see their similarities and differences. If two samples have a certain number of DNA markers in common, the people involved may be related. This is the basis for genealogical genetic testing. This is also the basis for forensic use of genetic testing. Typically, a DNA sample found at the scene of a crime is compared to that of a suspect. If they match, the suspect (or his or her twin) was at the scene.
Identity DNA testing is similar, but in this case the two samples being compared are typically from the same person, at two different times. The applications are usually on the unsavory side.
For instance, suppose someone works in an extremely dangerous occupation. In this case, they might want to store a sample of DNA against the day when their remains might have to identified using DNA.
In another example, have you ever seen those booths at fairs where parents are encouraged to fill out a card with their child’s name and other information, and take a DNA sample of their child, then store them in the fridge, just in case? Well, just in case of what? Suppose the unthinkable happends, and a child is kidnapped or disappears, how will the DNA in the refrigerator help locate or return the child? It can’t. The only thing it can be used for is to identify the child’s body, as in the example above. Not a nice thing to think about, but the service exists for people who would like to take advantage of it.
Identity testing can be used alongside DNA banking, where a DNA sample is stored in a secure location, and has passed through a chain of custody that will withstand scrutiny in court. One possible use for this service is to protect someone from fraudulent claims on their estate by people pretending to relatives.
