They have also appealed for more firearms.
Police have set up an office in Hokitika as they put renewed energy into the 27-year-old investigation.
The homicide investigation was launched after Mr Robinson's body was located at Bold Head beach, between Mikonui and Kakapotahi.
Since the beginning of the initial investigation, police have known he was shot once in the head with a .22 calibre firearm.
Detective Inspector Geoff Baber said yesterday they had never located the firearm that was used to murder David.
"As part of the reopened investigation, police have received a number of .22 firearms from individuals who owned them in the Kakapotahi area in December 1998.
"We are now able to conduct forensic examinations on these firearms so we can rule out any not used in David's murder," Det Insp Geoff said.
Police would like to hear from anyone else who owned a .22 firearm and was in the Kakapotahi area in 1998, or anyone who knew someone in the wider area who had such a firearm.
"For the purpose of our investigation, we ask for people to get in touch, let us know who may have these firearms now, and whether police could take them temporarily for the purpose of conducting a forensic examination."
They were also still looking for anyone who may have owned, used, or had seen a green 4×4 vehicle around 1998 in the Kakapotahi areas.
"It is not too late to provide David's family with answers — if you know something, we encourage you to come forward and speak with us."
Police reopened the case in mid-February.
A single gunshot was heard by numerous people in the settlement of Kakapotahi before Mr Robinson’s body was found.
This has also been part of the new investigation.
Any information that could assist police's investigation, email via the Cold Case form on the New Zealand Police website, or call 105 and reference the case number 231129/2221.
Greymouth Star
