Gerard Baden-Clay’s defence team says his wife could have drowned after falling or jumping from a bridge while under the influence anti-depressant medication.

Brisbane woman Allison Baden-Clay could have fallen or jumped to her death while under the influence of anti-depressant drugs, a court has heard.

Gerard Baden-Clay’s lawyer has outlined a possible explanation for the 43-year-old’s death as his client’s murder trial draws to a close in Brisbane.

Defence barrister Michael Byrne QC told the Supreme Court jury on Monday that in April 2012 Allison’s depression could have been triggered by discussion of her husband’s affair and recent news that his brother’s wife had borne a son.

The court has heard evidence that the mother to three girls had desperately wanted a boy to continue the Baden-Clay name.

Mr Byrne suggested Allison took an extra dose of her prescribed anti-depressant medication early on April 20, 2012, and went for a walk to clear her head.

He said at 4am the drugs would have peaked in her bloodstream and she could have been affected by known side effects such as confusion, disorientation or suicide ideation.

“At some time, for some reason, she ends up in the river,” Mr Byrne said.

“The autopsy report can’t rule out drowning, it can’t rule out a possible fall, a jump from a bridge which could have rendered her unconscious.”

Allison Baden-Clay’s body was found on a muddy bank under the Kholo Creek Bridge in Brisbane’s west on April 30, 2012.

The discovery was made 10 days after her husband reported her missing from their home in Brookfield, 13km away.

Former real estate agent Gerard Baden-Clay, 43, has pleaded not guilty to murder.

During his closing remarks on Monday Mr Byrne urged jurors to ignore “sensational” publicity surrounding the month-long trial and calmly weigh the evidence when considering their verdict.

He warned them against using moral judgments of Baden-Clay’s adultery to convict his client of the serious crime of murder.

“Maybe you would think that you find his morals despicable. That is a far cry though from labelling him a murderer,” Mr Byrne said.

The barrister used slides to highlight major gaps in the Crown’s circumstantial case, such as how Mrs Baden-Clay died, his client’s motive, and the lack of forensic evidence linking him to her death.

A small amount of Allison’s blood was found in the couple’s car.

“Why is there no blood anywhere in the house, outside the house, on the patio, in the carport, when the prosecution case is somehow the body is either dragged or carried through the foliage and deposited in the car?” Mr Byrne asked.

He also dismissed the testimony of several forensic experts who said marks on Baden-Clay’s face looked like fingernail scratches.

Mr Byrne said none of the experts could rule out 100 per cent that they were “shaving scrapes” from a blunt razor.

The barrister ridiculed claims his client had killed his wife because of financial pressure or plans to leave his wife.

Mr Byrne is expected to conclude his address on Tuesday morning before the prosecution delivers its final remarks.