CrimTrac, the agency which maintains the database, said yesterday a recent link-up between the Northern Territory and NSW was the last piece in the nation's cross-jurisdiction puzzle.

The puzzle has taken eight years to complete because of policy and legislative differences.

Now CrimTrac's chief executive Ben McDevitt is hoping to expand the database through broader DNA testing.

Mr McDevitt said the next step was taking samples from people charged but not convicted and from people charged for minor crimes as well as serious offences.

''I personally believe that newcomers to crime need to be added to the national DNA database as soon as possible,'' he said.

He said the majority of crimes were committed by a small proportion of the population.

''They are recidivist offenders, and in my view recidivist offenders need to be added to the national DNA database as early as possible in their cycle of offending.''

Mr McDevitt said he was opposed to mass DNA testing of the community.

Recent New Zealand laws meant people charged, or intended to be charged, with a serious offence can have a DNA sample taken when they are photographed and fingerprinted at a police watch-house.

Mr McDevitt said he supported a federal model expanding that to include ''volume crime'', including burglaries and car theft.

ACT and NSW already take samples from criminals convicted of a serious indictable offence.

In the ACT, a police officer can ask a person to submit to a DNA swab after they have been convicted.

The officer can apply for a court order should the offender refuse, but must have reasonable grounds for doing so.

Almost 600 profiles of serious offenders in the ACT were held by CrimTrac at the end of February.

The completion of the national database would result in more matches between criminals and crime scenes, Mr McDevitt said.

''This is a big step forward, and it's not only for implicating suspects, it's also about exonerating persons of interest and freeing up police resources,'' he said.

CrimTrac is preparing a discussion paper on the future of DNA testing.