A child-sex offender who believes giving a DNA sample would condemn him to eternal damnation wants an exemption from inclusion on a national police database.

David Hugh Chord, 37, appeared before Judge Peter Butler in Wellington District Court on Friday for a hearing to decide whether he will have to provide a DNA sample for a national database.

Chord is a Christian and believed that, if his DNA was taken, he would be given the "mark of the Beast" and damned for eternity, his lawyer, Michael Bott, said.

Chord is serving two years and nine months in prison after pleading guilty to six counts of an indecent act on a young person, and one of an indecent act on a child last year.

Mr Bott argued Chord's religious belief should exempt him from having to provide a sample for the database. "Based upon his interpretation of the Book of Revelation, that means he's effectively damned and cut off from fellowship with his God."

The law allowed people to be exempted from inclusion in the database if they would suffer serious harm when the sample was taken and, according to Chord's faith, he would suffer, Mr Bott argued.

Chord believed giving a DNA sample would cut him off from his God, and also the Christian community, which would impinge on his rehabilitation.

"Feeling damned after you have had a lifetime of faith is in fact serious harm ... My client will feel ostracised, he will suffer a loss of belonging, a loss of control, a loss of self-esteem, and will no longer have a meaningful existence."

Chord's DNA was not required to solve a specific crime, but rather to "bolster a database", Mr Bott said.

But Crown lawyer Kate Salmond said the issue was not whether there should be a database.

An objection to taking a sample had to be based on harm caused by the actual taking of the sample, and Chord had to show he would suffer "psychological harm resulting from fear for his mortal soul". Any exemption of Chord would be "unintended" by the law.

Judge Butler asked Mr Bott whether Chord's belief that anything that could identify him would inflict the mark of the Beast on him stretched to photos and fingerprints, which would have been taken when he was arrested.

Mr Bott said it did not, but was restricted to DNA, which was the clearest identifier of individuality. "It's accepted that DNA is the building block, the key, that shapes human identity."

Judge Butler went on to comment that any God that would damn someone for eternity because a DNA sample was taken against their will was a "pretty tough God or deity or supreme being".

Mr Bott agreed, but said that was Chord's belief.

Judge Butler reserved his decision.