Whooping cough fear hangs over Danny Klobucar murder trial

The loss of the ill woman has left the ACT Supreme Court trial with just 11 jurors, one less than the standard dozen, but the judge has ordered proceedings forge ahead regardless.

Klobucar, 27, is accused of beating a Canberra grandfather to death near the front door of his Phillip unit on New Year's Day 2014.

The trial has been running for almost three weeks, and is thought to have about another week of evidence and submissions remaining.

On Friday, a juror who has been struggling with a bad cough throughout the trial was revealed to have a suspected case of whooping cough.

The provisional diagnosis prompted concern in the court, given she has shared the confined jury room with her 11 fellow jurors.

The court is still waiting on tests to confirm the early diagnosis.

Justice Hilary Penfold told the jury on Tuesday that the sick 12th juror had now been formally excused.

She said anyone else who began to feel sick should seek medical help.

Justice Penfold said she was investigating whether the court could reimburse them for any unrecoverable medical expenses.

The trial then continued, first hearing from a psychiatrist who said he believed Klobucar was mentally impaired at the time of the alleged killing.

Klobucar is accused of murdering Miodrag Gajic, 71, two days after he first met him when he went to his Phillip unit to buy cannabis with his uncle.

Klobucar, who is said to have a tendency to believe older men were paedophiles, noticed Mr Gajic's Nissan Micra during the unsuccessful trip to buy drugs.

It is alleged he said the Micra was a "gay car" and that Mr Gajic was a paedophile, and probably had DVDs of him from his childhood.

On New Year's Day, the Crown alleged he went back to Mr Gajic's home and beat him to death, likely with a weapon.

It is alleged he left a bloody shoe print at the scene, which is said to match a Puma sports shoe found in his ute later that night.

He also allegedly took Mr Gajic's phone and made calls to a relative and friend.

Klobucar was arrested that night after a disturbance at the Lighthouse pub in Belconnen.

Klobucar is denying he caused Mr Gajic's death, and wrote a letter to a psychiatrist saying that Mr Gajic was already dead when he got there.

He is also relying on a defence of mental impairment.

Professor Andrew Carroll, a forensic psychiatrist, told the court on Tuesday that he diagnosed Klobucar with paranoid schizophrenia, and believed the accused was mentally impaired at the time of the killing.

Professor Carroll is the second of three psychiatrists who have found Klobucar was mentally impaired and could not properly understand the wrongfulness of his actions.

He said Klobucar's delusions – which included that he was an undercover police officer busting underground paedophile networks – meant he was unable to reason with a moderate degree of sense and composure that his actions were wrong.

That's because he thought his actions were justified because he was opposing a "very evil and dangerous paedophile ring".

Later on Tuesday, the court heard from Klobucar's uncle, Vito Le Clair.

Mr Le Clair said he sensed no negativity between his nephew and Mr Gajic when they went to the unit to buy drugs on December 30.

He said Klobucar was calling and texting him asking Mr Gajic's address the next night. Mr Le Clair said he didn't want to give his nephew the address because he was concerned about his behaviour.

The trial continues on Wednesday.