Prosecutors in the trial of Gerard Baden-Clay have speculated that he killed his wife to avoid his double life being exposed.

Brisbane man Gerard Baden-Clay wanted to “wipe the slate clean” when he violently murdered his wife amid fears his double life would be exposed, a court has heard.

Jurors are expected to retire to consider their verdict in the 43-year-old’s murder trial on Thursday after prosecutors finished their closing remarks on Wednesday.

Crown prosecutor Todd Fuller told the Supreme Court that, on the night Allison Baden-Clay was last seen alive, her husband faced being exposed as a serial cheat, which would have had serious consequences for his marriage and business.

His wife of 14 years and his long-term mistress were due to attend the same conference the next day, April 20, 2012, the jury was told.

Alison Baden-Clay thought the affair was over but the prosecutor said Baden-Clay couldn’t live without his former employee, Toni McHugh.

Mr Fuller said the father of three had promised to leave his wife for Ms McHugh despite telling relationships counsellor Carmel Ritchie he wanted to work on his marriage and “wipe it (the slate) clean”.

The prosecutor said exposure of the affair would have placed Baden-Clay’s marriage in jeopardy, his home life, his relationships with his friends and family, and his struggling business, which his wife and friends were involved in.

“Perhaps he felt that he had no other choice, no other choice but to take his wife’s life,” Mr Fuller said.

“What would have been in this man’s mind as he carried that out to bring it all to an end?” he said.

“The double life, the daily deceptions, the risk to him of it all coming crashing down?

“Like he told Carmel Ritchie, he just wanted to wipe the slate clean.”

Allison Baden-Clay’s body was found on a creek bank at Anstead in Brisbane’s west on April 30, 2012, 10 days after her husband reported her missing from their home in nearby Brookfield.

Baden-Clay has pleaded not guilty to murder.

The prosecutor told jurors they might think it “highly unusual” that Baden-Clay cut himself shaving in a way that looked like fingernail scratches or that Allison’s blood was found in the couple’s car.

Several forensic experts have testified that marks on Baden-Clay’s cheek the day he reported his wife missing were consistent with fingernail scratches.

Referring to suggestions by Baden-Clay’s defence team, Mr Fuller said jurors might think it unusual that Mrs Baden-Clay fell to her death or drowned, when the autopsy had ruled out those causes.

In summing up the trial, Justice John Byrne told jurors they could consider a manslaughter verdict if they found Baden-Clay not guilty of murder.

He warned them that, if they thought the accused lied about the injuries on his face, they shouldn’t regard a lie as indicative of guilt.

The judge is expected to finish his summary on Thursday morning before the jury retires to consider its verdict.