INTERPOL HANDBOOK ON DNA DATA EXCHANGE AND PRACTICE

THE VALUE OF A NATIONAL DNA DATABASEA DNA Database relies on the principle that DNA obtained from the genetic materialof a person or from biological evidence that is left at a crime scene is available ona database for investigative purposes. The underlying principle of a forensic DNADatabase is that DNA from one source will give the same profile whether it comesfrom a crime sample or a reference sample.A DNA Database therefore contains genetic information, in the form of DNA profiles, asrecords for people and crime samples. For different identity purposes, a DNA Databasemay contain different indexes for different identity purposes: for suspects, convictedoffenders, volunteers, the general population, victims, police, laboratory personnel,local emergency staff (medical doctors, paramedics, firefighters etc), suppliers, missingpersons and their relatives, unidentified bodies and mass screens.A forensic DNA profile simply consists of a string of alphanumeric characters indicatingthe exact number of repeats at each of the STRs and information about the person’sgender. When the alphanumeric code in two complete DNA profiles match, analystscan infer, not conclude, that they could have originated from the same source. Theprobability of observing two identical, full DNA profiles in two unrelated people is verylow, less than one in a billion.When new DNA profiles are loaded onto a DNA Database, the computer softwarecompares these new profiles with the existing ones. A search will reveal any matchesbetween the profiles added and the ones already present. Once this information isverified, it is then communicated to the investigating officer, purely as intelligenceinformation.An exclusion (non-match), inclusion (match), inconclusive or insufficient DNA resultcan be obtained (see In the Laboratory).•use of the resultsDNA profiling, like other scientific evidence, can only indicate an association betweenthe perpetrator and the crime. Therefore, any results require investigative police workto provide evidence and support the circumstances of the case. Consequently, all DNAresults should be interpreted within the context of the case and with an understandingof the factors that will impact on the results.In most countries, the custodian of the DNA Database is the Ministry of Interior,a State laboratory, or Special Police Force. The success of a DNA Database as aninvestigative tool is directly dependent on the number of DNA profiles it contains aswell as a laboratory’s capacity to analyse the biological evidence.THE VALUE OF A NATIONAL DNA DATABASE PAGE 57