Databases of DNA profiles

19 Apr

Databases of DNA profiles

Several countries have developed national DNA databases that contain large numbers of DNA profiles – the UK and the USA national DNA databases now both contain the DNA profiles of over 3 million individuals. DNA databases that store STR profiles have emerged as a powerful tool in the investigation of crime. The effective use of the DNA database, in particular in the UK, has acted as a catalyst for the establishment and expansion of DNA databases in other countries, including the USA and many European countries that now have databases with hundreds of thousands of profiles stored in them. This chapter will examine the development and application of the UK national DNA database, which is the first and most extensive database of its kind. It will briefly examine the development of databases worldwide.

The UK National DNA database (NDNAD)
The UK NDNAD was established in 1995 [1], shortly after STR profiling using six STR loci (the SGM) was introduced into criminal casework.

Rationale for criminal databases in the UK
There are several justifications for the time, effort and money that a criminal DNA database consumes:

Criminals tend to re-offend – 90% of rapists have had a previous conviction; 50% of armed robbers have a previous conviction.

The severity of crimes often increases — in many instances criminal activity starts at a young age with many criminals committing their first offence between 16-19 years of age.

A small number of criminals can be responsible for a large number of crimes – linking these crimes together can aid police investigations. This is particularly the case for burglaries, auto crimes, and serious cases such as sexual assaults.


TheUKDNAdatabasedidnotrequirespecificstatutesforitsestablishmentalthoughthe police service launched the national DNA database at the same time that the provisions of the Criminal Justice and Public Order Act 1994 came into force on 10th April 1995. Subsequent legislation has increased the scope of samples that may be collected and retained on the NDNAD (see next section).

Legislation in England and Wales 1994 The Criminal Justice and Public Order Act Within the UK the Police and Criminal Evidence Act 1984 (PACE), which governs the taking of samples from persons suspected of criminal activity, was amended to reclassify saliva and mouth swabs as non-intimate, thus allowing the samples to be collected without consent and without the need for a medical practitioner. 1997 The Criminal Evidence (Amendment) Act This allowed non-intimate samples to be collected from inmates currently in prison but convicted of an offence prior to the establishment of the NDNAD. 2001 Extension to the Police and Criminal Evidence Act 1984 (PACE) This allowed samples to be retained indefinitely irrespective of whether the person was acquitted at trial and from samples obtained from volunteers taking part in mass screens, provided that these volunteers gave their consent. 2003 Extension to the Criminal Justice Act Section 63 of the Police and Criminal Evidence Act (1984) was amended to allow the police to take a non-intimate sample from a person in police detention who has\ been arrested for, charged with, informed they will be reported for, or convicted of, a recordable offence. These powers came into force in 2004.

Criteria for entry onto the UK NDNAD

The original criterion for addition of a sample from an individual to the National DNA Database was that the person had been arrested for an offence punishable by imprisonment. If the person was found not guilty at a subsequent trial, or the case was discontinued, then their profile would be removed. In 2001 the Criminal Evidence Act allowed samples to be retained on the NDNAD, even if the individual was not found guilty. The regulations were further relaxed in 2003 with the Extension to the

Criminal Justice Act. Calls have been made in the UK by police chiefs and politicians for everybody to be entered onto the NDNAD – this prospect is still some way in the future.

Technology Underlying the NDNAD
The development of STR profiling was essential for the successful implementation of a large-scale DNA database. Attempts had been made to construct databases of VNTR profiles, and these did produce some successes. However, the difficulty of comparing VNTR profiles was a major limitation. STR profiles can be digitized very easily and this has allowed for the effective computerization of DNA profiles. The UK NDNAD was established using the SGM multiplex, which analysed six STR loci and the amelogenin locus. The match probability of SGM was 1 in 108 of the population, which for a population of 58 million within the UK was deemed acceptable. However, when six loci were used there were a number of coincidental matches (see below).

Adventitious Hits
In 1995 Raymond Easton was asked to donate a DNA profile as part of an investi-gation into a domestic dispute. Four years later a burglary at a home approximately 200 kilometres from where Raymond Easton lived generated a DNA profile that was compared to the NDNAD. This profile matched that of Raymond Easton and he was accused of the crime. A match probability of 1 in 37 million was reported. At the time of the burglary, Raymond Easton was suffering from Parkinson’s dis- ease and was unable to walk more than 10 metres unaided. This was an example of an adventitious hit. The test was conducted using the SGM loci, but the chance that a similar adventitious cold hit will occur has been reduced greatly by extending the test to ten loci.

In 1999, the six-locus SGM test was changed to the ten locus AmpFISTR®  SGM Plus®  test. The chance that two DNA profiles from unrelated people will match at all ten loci is less than 1 in 1 billion. To date no two people have been found to match at all ten loci; matches to two or more people can occur if a partial DNA profile is searched against the NDNAD.

Operation of the NDNAD
The NDNAD has two main sets of data: profiles generated from evidence that has been collected from crime scenes (263000 at the end of 2005 [2]) and profiles generated from individuals (3.45 million at the end of 2005 [2]).

Figure 10.1 Following entry onto the database the new samples are searched against all other samples on the NDNAD. Suspect-to-suspect matches will only occur when individuals have given incorrect details to the police about their identity unless a coincidental match occurs – to date no coincidental matches have been reported with a full SGM Plus DNA profile

A biological sample from a scene will be collected by the scene-of-crime officers and submitted for DNA analysis. The resulting DNA profile will be compared to those currently held on the NDNAD and if there is a match then this will be reported back to the police force that collected the sample (Figure 10.1). A fresh sample from the individual to which there was a match will be collected and the DNA analysis will be repeated. While the intention had been to use the NDNAD to match samples from seri- ous crimes such as sexual assaults and murders, the addition of samples from high volume crime such as burglary resulted in an increase of DNA profiles on the ND- NAD. In an average year the NDNAD produces around 40000 crime scene to in- dividual matches: the majority of these are high volume crime but there are invari- ably matches to more serious crimes such as murder, rape and assaults [2]. With such a large number of DNA profiles held on the NDNAD there is currently a 45% chance that a DNA profile obtained from an incident will match a DNA profile on the NDNAD [2]. In the UK, approximately 1 in 20 people are on the NDNAD; this includes 8% of the malepopulation[2,3].EthicalconcernshavebeenraisedthattheNDNADdiscriminated against vulnerable sections of society – 75% of young black males between the ages of 15 to 34 are on the database whereas only 22% of white males in the same age bracket are found on the NDNAD.

Familial searching
Familial searching was devised by the Forensic Science Service of the UK and is used when there is not a full DNA profile match between the crime scene and the NDNAD samples but a match is achieved at 15 or more alleles and the perpetrator most likely lived in the vicinity of the incident. While the person on the NDNAD can not be the donor of the sample obtained from the incident, it is highly likely that the originator of the sample is a relative of this person.

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