Jurors heard opening arguments Monday in the landmark trial of an HIV-positive man, accused of first-degree murder in the deaths of two women he allegedly had unprotected sex with.

It is the first time an HIV case has led to murder charges.

The Crown prosecutor said Johnson Aziga, 52, first learned he was HIV positive in 1997 but continued to have unprotected sex without disclosing his condition to his partners.

Aziga was first arrested and charged with 11 counts of aggravated sexual assault in 2003.

He was accused of having unprotected sex with at least 11 women without disclosing his HIV-positive health status.

However, two of those charges were elevated to first-degree murder after two of the 11 women later died from an HIV-related cancers-- one in December 2003 and the other in May 2004.

The two women he is accused of killing were from Toronto. For the first time ever, the jury will be able to hear from the murder victims. In the weeks before they died they recorded their testimony -- one on videotape, the other on audiotape.

Of the remaining nine women, five of them have contracted HIV.

"One may immediately think of a violent rape scenario," prosecutor Tim Power told the jury. "That is not what this case is all about."

Even though the sex between the man and the women was consensual, prosecutors said in fact, the women's consent is void because they didn't know they were having intercourse with someone who is HIV positive.

Davies Bagambiire, Aziga's lawyer, told reporters outside the courtroom that he plans to challenge "each and every aspect" of the allegations.

"We are sorry for the families," he said. "But we do not believe it can be shown beyond a reasonable doubt that the deaths emanated from the HIV virus."

In 2005, an Ontario Court Judge ruled there was enough evidence to make Aziga stand trial on murder charges.

"It's going to be a landmark case," Bagambiire said in an interview with The Canadian Press on Sunday.

"This is the first time that a Canadian is prosecuted for alleged murder through the alleged dissemination or transmission of the HIV virus."

Alison Symington, with the Canadian HIV/AIDS Legal Network, said there are about 60,000 people in Canada living with AIDS.

Symington said the case against Aziga is rare and the attention the trial will receive will likely increase stigma and discrimination against those with HIV.

She said the best way to protect the public is through education so that HIV-positive people feel comfortable telling their partners about their status.

"Condoms, disclosure: that's going to prevent transmission. Criminal charges aren't," she told CP on Sunday.

Aziga, from Hamilton, Ont., worked as a staff analyst with the Ontario Ministry of the Attorney General. He was diagnosed with HIV in 1996.

Earlier this month, Clato Mabior, an HIV-positive man from Winnipeg, received a 14-year prison sentence on six counts of aggravated sexual assault and one count each of invitation to sexual touching and sexual interference.

None of the half-dozen females -- ranging in age from 12 to adults -- Mabior had sex with became infected.

In another case, Carl Leone was sentenced to 18 years in prison last April after pleading guilty to 15 counts of aggravated sexual assault after failing to tell his sexual partners of his HIV status. Five of the 15 women he had sex with are now HIV positive.

In 2007, former Saskatchewan Roughrider Trevis Smith, who is HIV positive, received more than five years in prison for aggravated sexual assault.

He was found guilty of knowingly exposing two women to HIV.

With files from The Canadian Press