"They're obviously from people who are opposed to the law change I'm seeking. They're obviously not very bright, because they glued all the letters, but hand-wrote the address on the envelope," he said.
"It's so cowardly. It's totally the opposite of what religion represents. Anyone who offers a religious view tainted with threats ... would make you question their moral and religious integrity."
Senior Sergeant Kelvin Lloyd said Dunedin police were taking the attack and death threats seriously.
"The potential for serious injury is obvious, with ... the weight of a brick, and the perpetrator couldn't have known if anyone was on the other side of the window." Inquiries were continuing, Snr Sgt Lloyd said.
Davison was convicted and sentenced to five months' home detention in October for aiding the death of his terminally ill mother, Dunedin doctor Patricia Elizabeth Davison (85), after he wrote a book, Before We Say Goodbye, revealing he administered morphine to his mother, at her request, in 2006. The term was to be served at the Kaikorai home of friend John Landreth, who was shocked at the attack.
"I'd normally be sitting on the couch by the window at that time. If I had been sitting there on Friday night it could have killed me," Mr Landreth said yesterday.
"I'm angry the details of the address were revealed in court. It's a breach of my privacy."
However, the threats have only strengthened Davison's resolve to help reform euthanasia laws.
"There has been so much support from people. In five or 10 years' time, when the law has been changed, we'll be talking about how we ever allowed that to happen," he said.
"If I'd got the death threat in South Africa, I'd have been genuinely concerned. But it's difficult to take threats like this seriously in New Zealand."
The offender picked the wrong target in Davison, who is head of the University of Western Cape forensic DNA laboratory in South Africa.
"I'm going to get the letters DNA-tested at our laboratory in Cape Town ... you can easily get profiles from stamps and envelopes," he said.
"Then I'll provide the results to the police."