Steven West.JPG

Steven West on trial for the 2012 murder of Alyssa Haden.

(Lindsay Corcoran | MassLive.com)

WORCESTER - On the night she died, the man charged with Alyssa Haden's murder says she asked to be tied up, with her face down in a pillow during sex.

That's how Steven West, 24, who weighed in excess of 400 pounds at the time, says his wife's 20-year-old twin sister died "accidentally."

West's trial in the 2012 killing of the Spencer woman began in Worcester Superior Court on Monday.

Attorney Gavin Reardon claimed Haden had an ongoing sexual relationship while she lived with her sister, West and their young son.

"Alyssa had unusual sexual interests," Reardon said.

Attorneys said evidence will show that Haden died of suffocation, partly from having heavy weight on her, on the night of Oct. 9 into Oct. 10, 2012.

In a Nov. 1 interview, West allegedly told police Haden asked to have her arms tied behind her back and her face down in a pillow. He said she died in that position.

West also allegedly admitted to police that he redressed her then left to go to McDonald's before visiting his pregnant wife in the hospital.

Assistant District Attorney Brett Dillon said there is no evidence that Haden was having an ongoing sexual relationship with West. He pointed out that she had a boyfriend, with whom she was texting on the night of her death.

Dillon argued that the type of sexual activity Haden consented to with her boyfriend wasn't "evidence she agreed to sexual acts" with West.

"This wasn't consensual sex. This wasn't an accident. The evidence will conclude that this was rape. That this was murder," Dillon said.

Prosecutors also outlined how Haden's phone was missing when police began investigating her death and how West later admitted to taking it.

"He says he took it, put it into pieces and threw it out the car window on his way to McDonald's," Dillon said.

Reardon admitted that his client lied about the circumstances, "bizarrely and explicitly" for months.

The trial for West is expected to last a week.