By Andrea Lucia

DALLAS (CBSDFW.COM) – More than three-and-a-half years after his arrest, one of the worst accused serial killers in Texas history finally went to trial Monday morning, Nov. 15.

Billy Chemirmir is accused of killing at least 18 elderly women in North Texas, smothering them in their own homes and stealing their jewelry, but in his first trial, he faces a single count of capital murder for the killing of 81-year-old Lu Thi Harris.

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Lu Thi Harris (credit: Harris family)

The most striking testimony came from a video deposition of then 92-year-old Mary Bartel, one of only two women investigators say survived his attacks. Bartel, who passed away last year, didn’t live long enough to see Chemirmir in court.

“I heard this very insistent rapping at the door,” she told an attorney questioning her.

She recalled opening the door to a man who forced his way inside.

“I knew instantly, when I saw those two green rubber gloves, number one I should have not opened the door and two my life was in grave danger.”

Bartel said the man warned her, “Don’t fight. Lie on the bed.”

Then, she said, he grabbed a pillow.

“He just smashed the pillow down hard over my face and my chest and I just couldn’t breathe,” she said.

When Bartel later regained consciousness she realized her jewelry, including a gold wedding band and a diamond engagement ring she’d been wearing, were gone.

She was able to identify them in pictures that appeared to show them posted for sale online.

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“Lots of tears,” said Loren Adair, the daughter of alleged victim Phyllis Payne, describing the scene in a room upstairs.

Family members of 10 murder victims linked to Chemirmir gathered there to watch the first day of trial together.

Billy Chemirmir murder trial (CBS 11)

Bartel, they said, who appeared mentally sharp and quick witted in her deposition, represented their mothers well, but her testimony was difficult to listen to.

“To know that that is what your mom went through, as well, that’s hard,” said Cheryl Sandburg, the daughter of Marilyn Bixler.

“Our moms probably thought the same things – why did we open the door to this man,” said Adair.

A detective investigating Bartel’s attack testified he found a report of a suspicious vehicle at the complex and traced it to Chemirmir.

Plano police went to his apartment complex to arrest him on an unrelated DWI warrant.

Officers testified they found him holding jewelry.

In a nearby dumpster he’d approached, they discovered a jewelry box with paperwork inside with the names of the victim, Lu Thi Harris and her late husband.

The defense opted not to give an opening statement and has had few questions for the witnesses, so far.

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During Bartel’s video deposition, they brought up her inability to get a good look at her attacker.