DATABASES

• Jurisdiction: Australia

Introduction ................................................................................................... [82.1300]

Familial searches .......................................................................................... [82.1320]

[82.1300] Introduction

A large portion of work carried out in any forensic DNA facility will be on crime where no suspect has been nominated. These cases are sometimes referred to as volume crime (although this term often encompasses minor crimes where suspects are nominated) or database cases. The aim of submitting samples in database cases is for a DNA profile to be obtained from the offender, which can then be used as investigative information to assist in criminal investigations.

To assist in this endeavour, forensic laboratories utilise searchable DNA databases. DNA databases are essentially large lists of DNA profiles. Whenever a DNA profile from an evidence item is obtained, it is added (or typically referred to as "uploaded") to the database of profiles. Also added to the database are all reference samples from convicted offenders, suspects of a criminal investigation, persons of interest, unknown deceased individuals or volunteers. It is typical for each forensic laboratory to hold a local database and for each local database to be combined to form a national database. Searches are conducted at regular intervals among all DNA profiles held on the DNA database in accordance with state or federal legislation. Legislation will dictate which groups of samples can be compared; for example, DNA profiles obtained from evidence items may be able to be compared to references samples from convicted offenders but not unknown deceased individuals.

DNA profiles uploaded to the database do not need to be complete (ie, they do not need to possess a full complement of alleles); however, the more information that is missing from the DNA profile, the lower its discrimination power will be. A lower discrimination power means that when the profile is searched against others in the database, there are likely to be numerous matches, not to the true source of the DNA obtained from the evidence item, but to individuals who happen to have the same partial DNA profile. These matches to individuals unrelated to the crime are known as adventitious matches. To avoid such adventitious matches, there are typically business rules that surround the type of profiles that can be uploaded and the level of information that must be present in a...