A formal extradition request has been made to the Kenyan Government for a man wanted for a Christchurch murder and attempted murder.

Samuel Njuguna is wanted for the alleged attempted murder of his estranged wife Lydiah Munene and the alleged murder of Steven Maina in Christchurch last year.

Detective Inspector Greg Williams, head of the investigation, said authorities have been working on extradition proceedings since a warrant for Njuguna's arrest was issued in October last year.

"The New Zealand Government has made a formal extradition request to Kenya, seeking the return of Mr Njuguna," he said.

"MFAT officials, New Zealand's honorary consul in Nairobi and NZ Police have been liaising with the Kenyan government about this case. This has included diplomats based in Pretoria visiting Nairobi, and our honorary consul pursuing the matter with the Kenyan police and prosecution service."

Kenyan officials are now looking for Njuguna and once he is found, the extradition request will be dealt with in accordance with Kenyan law, says Mr Williams.

"As is the case here, extraditions in Kenya involve a judicial process, which can be time-consuming."

But there is no need for an extradition treaty between Kenya and New Zealand in order for Njuguna to be extradited, says Mr Willaims.

"Without pre-empting any judicial process, we are hopeful that, once located, Mr Njuguna will be extradited to New Zealand without undue delay."

Ms Munene, 35, was found with critical head injuries in her Christchurch flat alongside the slain body of friend Stephen Mwangi Maina, 38, in September last year.

It is alleged that Njuguna entered Ms Munene's house on September 12, where he murdered Mr Maina and attempted to murder Ms Munene.

Police say a weapon was used, but will not disclose what it was.

Investigators have found Njuguna left New Zealand at 1pm the following day, before Mr Maina and Ms Munene had been found.

Ms Munene and Mr Maina were only discovered by a concerned friend on September 14, two days after the attack.

Police were able to contact Njuguna's family within days of beginning an investigation.

Mr Williams said the family wanted to help investigators, and had even booked a plane ticket so Njuguna could return to New Zealand to face charges.

"His family there felt that he should return to New Zealand and be held accountable. The family purchased a plane ticket for Mr Njuguna and he was due to return but at the last minute decided not to."

That led to Christchurch District Court issuing a warrant for Njuguna's arrest on charges of murder and attempted murder in October 2009.

A formal extradition request was constructed by multiple national and international agencies including Crown Law, Crown Solicitors, Interpol and the Ministry of Foreign Affairs, Mr Williams said.

Victim thankful to be alive

After Ms Munene was found, she was taken to Christchurch Hospital's intensive care unit and placed in an induced coma.

Part of Ms Munene's skull had to be removed to relieve pressure on her swollen brain, and she now has a titanium plate in her head. She had to re-learn the English language which she lost after the trauma to her brain.

Ms Munene, who moved to New Zealand six years ago with her husband and children, said she had no memory of the attack.

"I know what was done to me, but I don't have any memory of that day, she told the Herald in September this year.

"I don't think about the past. I'm just thinking about my kids. It's a gift to be alive," said Ms Munene, who is mother to Michael, 14, and James, 9.

"And that is why I have become a very positive person ... Once you forgive and forget, you just start getting other good things following you."