Police in Perth are investigating the death of a man who was waiting to be sentenced for the mercy killing of his severely disabled partner.

Herbert Erickson, 81, drowned at the city's Floreat Beach late last night.

His vehicle was found in the car park and his clothes were folded neatly on the beach.

Erickson pleaded guilty on October 31 to murdering his 73-year-old partner, Julie Betty Kuhn, by smothering her with a pillow at their Armadale home in January.

The court was told Erickson was deeply in love with his partner but could not watch her suffer.

He was Ms Kuhn's carer for several years after she suffered a stroke and was confined to a wheelchair.

The Supreme Court was told Erickson was honouring a pact with his partner not to go into a nursing home.

After smothering Ms Kuhn, the elderly man tried to electrocute himself but survived, despite suffering severe burns and losing the index fingers on both hands.

He was released on bail to be sentenced in January.

When he left the court, Erickson told the media: "I don't want to go to jail, I want to be with my partner, but I'm here, worst luck."

His lawyer, David Manera, described the killing as a love story.

"This was an offence committed not for any gain by Mr Erickson," he said.

"He dearly and deeply loved his partner and it's not a situation where I say he stood to gain anything."

Speaking this morning, Mr Manera says it was not a simple murder-suicide.

"In many respects it was an act of love, in both what he was charged with doing and ultimately what he did to himself," he said.

"I think it's an absolute tragedy because we were hopeful that we would be able to convince the court not to impose a term of imprisonment.

"And, that he could live out the rest of his life a free man albeit subject to whatever punishment the court would consider appropriate."

Police have described Erickson's death as a tragedy and say a report will be prepared for the coroner.

Voluntary euthanasia

Mr Manera says the case will renew the debate on voluntary euthanasia.

"Bernie Erickson, first and foremost, loved his partner more than any of us, I suppose, could ever imagine," he said.

"And it would seem his main concern when he took his own life was his love for others, namely his family, and being a burden on them."

Euthanasia campaigner Philip Nitschke says politicians should hang their heads in shame over the death.

He says it is obvious to everyone that Erickson was acting out of compassion.

"I think it's a tragedy and it's a damning indictment of our governments at state and federal level, who refuse to address this issue," he said.

"We've got people who are desperate to try to help people they love have a peaceful death, and when they do try and do that and they perhaps get it a little wrong, they're then made to suffer because of the laws of the land.

"Then of course when they are made to suffer, they then have to take this final step to be with that person they loved so much."

'Blood on their hands'

Dr Nitschke says politicians should realise something has to change.

"I think the politicians of the nation have the blood on their hands of deaths like this," he said.

"I hope [they] realise that something has to change.

"We've got to have decent legislation in place which allows people who are suffering, the option of a peaceful, lawful death."

The State Opposition leader, Mark McGowan, has spoken out in favour of voluntary euthanasia.

"If people are terminally ill, they are in great pain and they make a choice personally to end their suffering, well then I would support them," he said.

"That means I would vote for a bill that provided that opportunity.

"That's my view and I have a different view to lots of people in our community."

Premier Colin Barnett has described the situation as very sad, but he still does not believe euthanasia should be legalised.

"I know many people support that, I don't, and I don't think many members of parliament do," he said.

"It does amount to a legalised killing and it raises a whole lot of other issues, I think - caring for people in their dying days is best left to the doctors and the family.

"I understand there have been calls for euthanasia for years and I'm sure it'll go on.

"There is probably only one country in the world that allows it, so it suggests that policy makers and governments around the world do not think that's the way to go."