Murderer David James Lothian has been given another jail sentence, for trying to blackmail a man he did not know was dead.

However, Lothian won't have to spend extra time in prison for his latest offence – he is already serving a life sentence, so the new jail term cannot be added on the end. It will instead be served concurrently.

Lothian and a co-offender, James Taylor Martin Webby, were convicted in 2019 of the murder of Napier man Alex Latimer at Te Haroto on the Napier-Taupo highway the previous year.

Lothian was in Hawke's Bay Regional Prison for that killing when, on 14 May 2020, he wrote a letter threatening a man named Nind.

Lothian wrote that he had a copy of a statement that Nind had made to police, detailing Lothian's involvement in an aggravated robbery.

He wrote that if Nind did not start putting money into a prison bank account, that information would be shared among Lothian's associates, "or indeed anyone he could have the opportunity of speaking to", according to Napier District Court Judge Gordon Matenga.

"The implication was that Mr Nind would become known as a nark," Judge Matenga said.

Lothian demanded a total sum of $3000, to be paid in instalments to the prison bank accounts of Lothian and an associate.

What he did not know when he wrote the letter was that Nind had died.

Lothian sent the letter through the prison postal system. Prison authorities opened it, read it, and referred it to police, who charged Lothian with attempted blackmail.

Lothian was found guilty at a judge-alone trial in November last year and Judge Matenga has now sentenced him to 21 months of imprisonment.

Although Lothian is already serving life with a non-parole period of 20 years, Judge Matenga said Lothian needed to be held to account for the attempted blackmail.

"The principles of denunciation and deterrence are factors which need to be considered."

After receiving submissions from Crown solicitor Michael Blaschke and defence counsel Will Hawkins, Judge Matenga said he did consider the point that this had been a "victimless crime".

But he said this did not matter.

"When Mr Lothian posted the letter he had no idea that Mr Nind was deceased."

Lothian and Webby murdered Latimer, whom they knew through the Hawke's Bay drug scene, on September 30, 2018.

The High Court was later told that they beat Latimer, then threw a shovel at him and told him to dig his own grave before stabbing him multiple times.

High Court Justice Robert Dobson said that the two murderers had dealings with Latimer only in the context of dealing drugs.

"But he had another life in a close-knit family where he gave considerable love and support, and your brutal killing of him was entirely unprovoked."

Judge Matenga's sentencing notes revealed that Lothian, a father of seven, has cancer.

"That (cancer) is currently in remission but that, of course, could change at any time."