Mr Karam and Mr Laws went head-to-head to debate evidence raised at David Bain's retrial, where he was found not guilty of murdering his parents and three siblings in their Dunedin family home on June 20, 1994.
At the trial last year, Mr Bain's defence team said Robin (58) shot his family before turning the rifle on himself.
The debate at one point turned into a shouting match when the pair were discussing blood stains on Robin's hands and a scratch above David Bain's eye.
"You're very loose with words, Michael," Mr Karam said.
"If you banged into the door, that is exactly what you would have."
Mr Laws responded: "Except David didn't say that was the reason, which is the reason you did not put him on the stand".
Mr Karam said to Mr Laws: "I hope this is not about winning for you. You're an intelligent man."
Mr Laws told Mr Karam: "You do not want to hear the truth".
Mr Karam said there was blood smeared on Robin Bain's hands.
Mr Laws said: "That is a lie, Joe Karam".
Later, Mr Karam said blood found on Robin Bain's hands was never tested by police.
Mr Laws cut in: "You've shown me the murder scene. There is blood smeared everywhere - up the curtains, up the walls."
Mr Karam responded: "Stop, stop, stop. The blood smeared on the curtains are all drops not smears ... his hand did not go wandering after he died".
Mr Karam said: "You don't just freeze either."
He said Robin Bain was also found with a sizeable bruise on his knuckle.
"Imagine if David had a bruise on his hand. You would be crying from the rooftops," Mr Karam said.
Mr Karam said anything Mr Laws did not like about the evidence, he labelled an "invention".
"You are calling me a liar," Mr Karam said.
Mr Laws responded: "No, I am not".
Mr Karam was asked by a RadioLive listener why a series of "cryptic clues" was left if Robin Bain had been the killer.
Mr Karam said most suicidal and murderous behaviour was irrational.
He said Robin Bain was reacting to "dreadful allegations" he had been having an incestuous affair with his daughter.
Earlier, Mr Laws told listeners there was only one person who could possibly have murdered the Bain family and that was David.
Mr Laws said the debate was back in the public because David Bain was seeking compensation after being jailed for 13 years.
"But there are at least 20 empirical forensic pieces of evidence that clearly demarcate David as the killer," Mr Laws said.
He said the jury did not get to hear suppressed evidence, which included a former friend of Mr Bain alleging Mr Bain had planned to use his paper round as an alibi for a rape.
He said Mr Bain was the only person who knew where the trigger lock keys were for his rifle.
"And why didn't David Bain take the stand in 2009?" Mr Laws asked.
"Because the last time, he effectively incriminated himself on the stand."
"If you hadn't murdered your family and you were innocent and had a sense of absolute outrage, why wouldn't you put yourself on the stand in 2009?"Brent Impey, the former boss of Mediaworks which owns RadioLive, chaired the argument.
Mr Impey said it was important to note David Bain was under no obligation to take the stand and was exercising his legal rights not to do so.
Mr Karam said it was clear from evidence presented at the second trial that Robin Bain killed himself and therefore killed the rest of the family.
He said Robin Bain's head wound was a contact wound because blood was found in the barrel of the rifle.
An argument broke out over finger-printing on the rifle.
Mr Laws said only David Bain's fingerprints were found on the gun.
Mr Karam said that was not the case.
"You have a view not shared by seven forensic experts at the trial," Mr Karam said.
He summed up by saying several pieces of police evidence had fallen over by the retrial, including DNA evidence linked to two pieces of skin found in Stephen Bain's bedroom.
Mr Karam said Robin was described by friends as dishevelled, "smelly and dirty" and was facing serious allegations of an incestuous affair with daughter Laniet.
Mr Laws said all the forensic evidence pointed to David Bain being the killer.
