A woman testified that she helped an Alberta man on trial for the deaths of three people clean what she assumed were bloodstains from his truck, the day after the slayings.

Kacy Lancaster, 22, testified Tuesday that she cleaned Jeremy Steinke's truck, assuming the stains on the seat was blood from a fight because he had a black eye at the time.

Kacy Lancaster leaves the Calgary courthouse on Tuesday. (Mike Moynihan/CBC)

Steinke, 25, is charged with three counts of first-degree murder in the stabbing deaths of his girlfriend's parents and brother, 8. Their bloody bodies were found in their Medicine Hat home on April 23, 2006.

The next day, Lancaster said she drove a friend home to Leader, Sask., about 480 kilometres east of Calgary. In the truck were six people, including Steinke and his girlfriend, who rode in the truck's covered cargo box.

Lancaster, who admitted she once had a crush on Steinke, testified that she included the couple because they "seemed bored," and that she didn't know about the killings at the time.

It was at a gas station that Lancaster said she saw a newspaper and discovered the girl's family had been slain.

Lancaster recalled that she was totally shocked, yet didn't call police. She said on Tuesday that she regrets "acting foolish."

Authorities found the group and arrested Steinke and the girl in Leader that day.

Before Lancaster took the stand, Court of Queen's Bench Justice Adele Kent cautioned the jury to weigh her testimony with great care and caution, because Lancaster herself faces a charge that's still before the courts.

Lancaster is charged with being an accessory to murder after the fact and has a court date next month.

Another girl, who was then 15, pleaded guilty to obstruction of justice and was sentenced to probation of 20 months.

Accused had black eye, friend testifies

Earlier on Tuesday, a witness testified that Steinke left his home and returned with a black eye on the morning of the slayings.

Mitchell Dayton, 19, told the jury that he spent the night of April 22, 2006, at Steinke's home in the Tower Estates trailer park in Medicine Hat.

Dayton said Steinke left in the middle of the night, and later returned with a "big black eye" and acted like someone who had just been in a fight.

He said Steinke showered and was putting things into garbage bags and a backpack.

According to Dayton, Steinke's girlfriend arrived in a cab early in the morning. Before the couple left together, Steinke told Dayton, "If anybody asks, you haven't seen me. I wasn't here all weekend."

In an audio recording of Steinke and an undercover officer played for the jury last week, Steinke is heard describing how his girlfriend's father attacked him with a screwdriver, hitting him in the eye. On the tape, Steinke says he then stabbed the man.

The Crown is trying to prove Steinke and the girl plotted the killings because her parents disapproved of their relationship, and then planned to run away together.

The girl, who was convicted of three counts of first-degree murder last year, is currently serving a 10-year sentence for young offenders.