Forensic testing of letters threatening the life of euthanasia advocate Sean Davison has failed to provide DNA evidence of who wrote them.
Davison is serving a five-month home detention sentence in Dunedin after pleading guilty late last year to aiding the 2006 death of his terminally ill mother, Dunedin doctor Patricia Elizabeth Davison (85), by acceding to her request for morphine.
He received the death threats last month, one attached to a brick thrown through the window of the house in which he was then staying.
Davison, the head of the University of Western Cape (South Africa) forensic DNA laboratory, sent a letter to the laboratory for analysis, while Dunedin police also had a letter forensically tested.
Davison yesterday said his forensics DNA laboratory was a world leader in the analysis of highly degraded DNA and "low copy number DNA", the type that would be present on the letters, but was unsuccessful in obtaining a DNA profile from them.
Detective Senior Sergeant Kallum Croudis, of the Dunedin CIB, said the police forensic examination of the letter had also revealed no clues that could lead police in a positive direction towards any person.
"We're still keeping an open mind on it. If anyone has any information that will help us they should let us know."
Davison said he had relocated to a new house and the court had agreed to keep that address confidential to avoid any repeat of the threatening incidents.