Alex Murdaugh didn’t help his defence when he took the stand at his trial for the murder of his wife and son, three jurors said on Tuesday.

Murdaugh’s testimony only managed to cement what they were already thinking — that he easily lied and could turn on and off his tears at will, the jurors said on the NBC Today show.

The key piece of evidence in finding the lawyer guilty, they said, was a video on his son’s mobile phone that was shot minutes before the killings at the same kennels near where the bodies were found at their sprawling estate in rural South Carolina.

Murdaugh’s voice can be heard on the video even though he insisted for 20 months that he hadn’t been at the kennels that night. Investigators didn’t see the video for more than a year before advances in hacking enabled them to unlock Paul Murdaugh’s iPhone. They shared it with the defence before the trial.

The jury deliberated for less than three hours before finding Murdaugh guilty. Photo / AP

When he took the stand, the first thing Murdaugh did was admit he had lied to investigators about being at the kennels, saying he was paranoid of law enforcement because he was addicted to opioids and had pills in his pocket the night of the killings.

“The kennel video, that just kind of sealed the deal,” juror Gwen Generette said.

Alex Murdaugh was sentenced for the murder of his wife and son. Photo / AP

The jury deliberated for less than three hours last Friday before finding Murdaugh guilty of killing his 22-year-old son, Paul, with two shotgun blasts and his 52-year-old wife, Maggie, with four or five rifle shots.

The now-disbarred lawyer maintained his innocence when he was sentenced to spend the rest of his life in prison for the murders.

Murdaugh was convicted in the same court circuit where his father, grandfather and great-grandfather tried cases as the elected prosecutor for more than 80 years. Murdaugh’s family founded the area’s most powerful law firm a century ago. For decades, that meant practically anyone who ended up in court on either side of the law in Colleton or Hampton counties would have a Murdaugh watching their back or staring them down.

His background was part of the reason jurors didn’t find his testimony believable.

“We already know that he’s a lawyer. He’s able to be emotional with cases. He’s able to be emotional with himself. He knows ... when to turn it on and off. So I think that we were able to read right through that,” juror James McDowell said.

Prosecutors decided not to seek the death penalty, and the judge handed down the harshest possible sentence he could — consecutive life sentences without parole.

Murdaugh admitted stealing millions of dollars from the family firm and clients, saying he needed the money to fund his drug habit. Before he was charged with murder, Murdaugh was in jail awaiting trial on about 100 other charges, ranging from insurance fraud to tax evasion.

Defence lawyers said they will base an appeal largely on the judge’s allowing jurors to hear evidence of crimes Murdaugh has not been convicted of, which they say smeared his reputation.

After six intense weeks at the courthouse in Walterboro, key players returned to their normal lives.

Prosecutor Creighton Waters, whose love of the guitar was a favourite bit of chatter among true-crime fans, tweeted a video of himself jamming. Judge Clifton Newman was seen in a courtside seat rooting for South Carolina to win the Southeastern Conference title in women’s basketball.

And defence lawyer Jim Griffin, admonished during the trial for tweeting an opinion piece criticising the investigation, returned to Twitter with a post that said “Walterboro, you were a gracious host. Happy Trails.” He included a photo of his head stuck through the hole of a painting of a cowboy riding a chicken, with “I was at the Murdaugh trial” written at the top.