Genetic genealogy utilizes DNA test results in conjunction with traditional genealogical research, to determine biological relationships between individuals.
When a person’s DNA sample is positively matched to their DNA “relatives” on a public genetic genealogy database, the genetic relationship can be determined (parent/child/sibling/half-sibling/first cousin, etc.). The range and degree of genetic relatedness is quantified by the amount of shared Centimorgans (cM), which is a unit that measures genetic relatedness.
For adoptees and other persons of unknown parentage, being matched to a half-sibling can prove parentage of either a father or mother, due to the fact that half-siblings share one biological parent.
For law enforcement purposes, the submission of a DNA sample of an unnamed perpetrator that returns useful DNA relative matches will typically lead the researcher to a common ancestor in a particular family lineage, providing a list of potential suspects. Using genealogy research tools such as family trees, census records, vital records, obituaries, newspaper archives, social media and online search engines, the researcher can then further narrow down the potential suspect list to a single suspect, through the process of elimination. This process can be painstakingly slow and tedious, but through persistent, methodical and systematic research, the probable suspect can be identified and named. Detectives must then surreptitiously obtain a DNA sample from the person identified through genetic genealogy to be compared to the DNA sample left at the crime scene by the perpetrator, in order to make a positive ID and arrest.
DNA relative matches can also be used to positively confirm the identity of unidentified deceased individuals by linking the DNA sample test results of the remains to the family or relatives of a missing person.