Lawyers acting for Robert William Pickton, on trial on six charges of first-degree murder, launched their defence Tuesday by attacking the credibility of the Crown's key witness, admitted cocaine user Lynn Ellingsen.

During earlier testimony in June before the B.C. Supreme Court in New Westminster, Ellingsen said she saw a dead person hanging from a chain in Pickton's pig slaughterhouse at his Port Coquitlam, B.C., farm.

Ellingsen also testified that she and Pickton had brought a prostitute to the farm earlier that evening.

But Pickton's defence lawyers responded Tuesday with testimony by four paramedics who were called to the Pickton farm during a two-month period in 1999.

On one occasion, when the paramedics arrived, Ellingsen complained about a sore shoulder and back pain. On another, she was feeling drowsy and sick after snorting a line of cocaine, the jury was told. But Ellingsen refused offers of treatment from the paramedics who were accompanied to the farm by a police escort.

The attempt to undermine Ellingsen's credibility came on the first day of the defence case in the Pickton murder trial. In his opening address to the court, defence lawyer Adrian Brooks said there are a great many things still to happen at the trial and "still a lot of brush strokes to add to the canvas."

IQ tests and school records will be among the evidence that the defence will present in the coming weeks, the jury was told.

The defence is also pledging to reveal the contents of the will of Pickton's mother, said Brooks, noting that Pickton's share of the estate was not released to the pig farmer until he reached the age of 40, at his mother's request.

Blood stains and the comings and goings of people will also be offered as evidence, said the CBC's Karen Tankard, who has been covering the case.

Pickton is on trial for the deaths of six women who went missing from Vancouver's Downtown Eastside between 2001 and 2007: Sereena Abotsway, Mona Wilson, Andrea Joesbury, Brenda Wolfe, Marnie Frey and Georgina Papin.

Pickton, who has pleaded not guilty, faces a total of 26 counts of first-degree murder in connection with the disappearances and deaths of women from Vancouver's Downtown Eastside. Six of the charges are being handled at the current trial, which began in January, while the other 20 charges are expected to be dealt with at a subsequent trial.

The prosecution wrapped up its case last month after calling more than 100 witnesses.

Among them was Ellingsen, who has admitted her memory was foggy due to longstanding addictions to drugs and alcohol.