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.


The UK DNA database did not require specific statutes for its establishment although the 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 investigation 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 disease 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 AmpF/STR® 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 (263 000 at the end of 2005 [2]) and profiles generated from individuals (3.45 million at the end of 2005 [2]).



Potential Matches:

- Crime scene to suspect

- Crime scene to crime scene

- Suspect to suspect

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 serious 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 NDNAD. In an average year the NDNAD produces around 40000 crime scene to individual matches: the majority of these are high volume crime but there are invariably 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 male population [2,3]. Ethical concerns have been raised that the NDNAD discriminated 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.

Familial searching

Craig Harman was the first person to be convicted of an offence following a link between a sample taken from a scene and a relative of the perpetrator. In March 2003, Craig Harman, then 19, was walking over a footbridge spanning the M3 motorway to the west of London when he dropped a brick onto passing traffic. The brick struck and broke the windscreen of a lorry, causing a fatal injury to the driver. The brick was examined for the presence of biological material, and fingerprints, and a DNA profile obtained. The DNA profile did not match in full with any person on the NDNAD but 16 of the 20 alleles matched a genetic relative of Craig Harman. A separate match between the sample obtained from the brick and a sample taken from Craig Harman after he was linked to the crime through the database resulted in a match and Craig Harman pleaded guilty to manslaughter.

Cold cases

Since the advent of PCR-based techniques it is now possible to obtain DNA profiles from old case samples. The application of low copy number (LCN) PCR has further increased the chance of obtaining DNA profiles from highly degraded material. Cases, such as those of murder, that have remained open from dates prior to the introduction of DNA typing can now be re-examined using either standard DNA testing or LCN in combination with the NDNAD. The current technology has allowed numerous cases to result in a conviction and therefore closure.

Cold cases

In 1969 Roy Tutill was a 14-year-old boy whose body was found in woodland near Leatherhead. He had been sexually assaulted and strangled. Samples collected from the body and the clothing of Roy Tutill were examined but blood group testing failed to give any satisfactory results.

In 2001 the UK FSS retested the medical swab extracts using SGM Plus and produced a partial DNA profile that was compared to the NDNAD. The DNA profile matched that taken from a Mr Brian Field who, 2 years earlier, had been stopped by police on a drink-driving offence and had donated a DNA profile. Further work was performed by the UK FSS on samples from the trousers of Roy Tutill that had been kept in the freezer and this gave a full DNA profile that matched Field. Field denied the charges at his first court appearance but pleaded guilty to murder when he appeared at the Old Bailey in November 2001.

Caution must be excercised when examining samples collected by crime scene operators prior to the advent of PCR-based techniques as it is unlikely that those handling the items will have taken the standard precautions to minimize contamination that are now standard practice.

International situation

Following the success of the operation in the UK, other countries developed their own DNA databases. For many countries there was aneed to enact special legislation leading to delays in the implementation of DNA databases [3].

New Zealand implemented a DNA database in 1996 along similar lines to that of the UK. The population is significantly smaller but as a percentage of the population New Zealand is second only to the UK in terms of the number of DNA profiles held on its database. Australia and South Africa were also rapid in developing DNA databases.

In mainland Europe, almost all countries have established DNA databases although all are limited in comparison to the UK version. The Netherlands and Austria established their version of a DNA database in 1997, with Germany following one year later and Finland and Norway in 1999 [5].

Two countries in the Middle East, Kuwait and the United Arab Emirates, are both currently developing plans that would see the entire population analysed and placed on a DNA database.

US DNA database

The US Army established a database of their own in 1992 to identify missing persons in operation Desert Storm and this experience helped to pave the way for a national database within the US. In 1994 the US congress passed the DNA Identification Act (Public Law 103 322) which enabled the establishment of the Combined DNA Index System (CODIS). The CODIS, which is the federally held DNA database, has expanded very quickly and comprises the National DNA Index System (NDIS), the State DNA Index System (SDIS) and the Local DNA Index System (LDIS). The information about each sample that is loaded onto the CODIS database includes a laboratory identifier, a specimen identifier, information to classify and review the integrity of the DNA record, and the DNA profile itself. CODIS links local, state and federal crime laboratories. The FBI selected 13 STR loci (CODIS loci) for developing the database. Like the UK NDNAD there are two main segments called 'indices' of CODIS:

• The Forensic Index contains DNA profiles from crime scene samples.

• The Offender Index contains DNA profiles of individuals convicted of certain categories of violent crime, though now many states are expanding their databases and are profiling persons arrested for all felonies.


Other CODIS indices are:

• unidentified human remains;

• relatives of missing persons.

All 50 US states now have databases of which only 13 obtain DNA samples for databas-ing for all felonies. At the moment there are about 180 DNA laboratories around the USA that are designated and accredited as CODIS laboratories. These laboratories are validated according to the standards of FBI and are authorized to submit the DNA profile information into CODIS.

The situation in the US as of late 2006 is:

total number of profiles: 3 676 971

total forensic profiles: 148 068

total convicted offender profiles: 3 528 903

When compared with the UK, the USA is a much larger jurisdiction but due to lack of funding, coherent structure and variable legal approaches, there are lengthy delays in DNA profiling of casework samples that has led to massive backlogs. The President of the USA announced the 'President's DNA Initiative' in 2003 in order to enhance and streamline the use of DNA as a forensic tool and also signed an act to enhance the facilities for DNA databasing [4]. The main aims of this initiative are to clear the backlogs quickly and also to improve the capacity of the forensic laboratories for databasing the samples besides promoting research and development in the field.

Cross-border databases

Criminals tend to operate in their own country but there are circumstances when crimes will be committed in more that one country. In order for criminal databases to be effective in these circumstances there is a need to share data. Interpol has been instrumental in facilitating cross-border comparisons of DNA profiles. The STR loci commonly used in the forensic community were combined to make the Interpol Standard Set of Loci (ISSOL); these have since been expanded from seven loci to ten loci [6]. Other organizations, such as the European DNA Profiling Group (EDNAP), are working towards the standardization of DNA profiling such that an organization in one country will be able to access DNA data in the database of another country. The biggest obstacle to cross-border data sharing is now political rather than technical.

WWW resources

Interpol (DNA front page):

Federal Bureau of Investigation (CODIS Information):

Association of Chief Police Officers of England, Wales and Northern Ireland: (National DNA Database report): GeneWatch UK:


1. Werrett, D.J. (1997) The National DNA Database. Forensic Science International 88, 33-42.

2. Parliamentary Office of Science and Technology. (2006) The National DNA Database.

3. Harbison, S.A. et al. (2001) The New Zealand DNA databank: its development and significance as a crime solving tool. Science and Justice 41, 33-37.

4. President's DNA Initiative. Advancing justice Through DNA Technology. (Vol. 2007)

5. Schneider, P.M. and Martin, P.D. (2001) Criminal DNA databases: the European situation. Forensic Science International 119, 232-238.

6. Gill, P. et al. (2006) The evolution of DNA databases - Recommendations for new European STR loci. Forensic Science International 156, 242-244.

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