Alex Murdaugh, a prominent South Carolina lawyer, was sentenced to life in prison on Friday for the murders of his wife and son on their hunting estate in a case whose twists and turns drew global attention.

Judge Clifton Newman sentenced Murdaugh, scion of an elite family of judges and attorneys, to consecutive life terms without parole for the June 7, 2021 murders of his son Paul and his wife Maggie.

Dismissing Murdaugh's claims of innocence as "not credible," the judge told the disgraced attorney he must "see Paul and Maggie during the night times when you're attempting to go to sleep."

"I'm sure they come and visit you," the judge said.

US lawyer Alex Murdaugh will serve a life sentence. Photo: AFP

"All day and every night," replied the lanky red-haired Murdaugh, who was dressed in a tan prison jumpsuit and wearing handcuffs and ankle shackles.

A jury in Walterboro, South Carolina, deliberated for less than three hours before finding Murdaugh guilty on Thursday after a six-week televised trial that gripped the nation.

Netflix and HBO rushed out documentaries on the case before it was even over.

Craig Moyer, a carpenter who served on the jury, told ABC News that Murdaugh came across as a "big liar" who did not show any "true remorse or any compassion."

According to the prosecution, Murdaugh shot his wife and son after realizing his years of stealing millions of dollars from his law firm and from clients to feed his hidden opioid addiction was about to go public.

The 54-year-old Murdaugh briefly addressed the court during the sentencing in a packed courtroom that included his surviving son, Buster, who testified in his defense.

"I'm innocent. I would never hurt my wife Maggie. And I would never hurt my son Paw Paw," he said, using his son's nickname.

"It might not have been you," the judge responded. "It might have been the monster you become when you take 15, 20, 30, 40, 50, 60 opioid pills."

Prosecutor Creighton Waters urged the judge to impose the maximum of life in prison on a man he called a "cunning manipulator."

"The depravity, the callousness, the selfishness of these crimes, are stunning," Waters said. "He violated the trust of so many, including his friends, his family, his partners, his profession, and most of all, Maggie and Paul."

During the sentencing, the judge noted that Murdaugh's family had "controlled justice in this community for over a century" and "many have received the death penalty -- probably for lesser conduct" than in this case.

Key video on victim's phone

Murdaugh's 22-year-old son Paul was killed with a shotgun and his 52-year-old wife Maggie with an assault rifle the family used to hunt wild pigs on their sprawling property.

While evidence put Murdaugh at the scene shortly before the murders, the guns were never found, and there was no bloodstained clothing or other direct evidence that could prove he was the killer.

But the jury determined the evidence was strong enough to convict Murdaugh on two counts of murder and two firearms charges.

Murdaugh testified in his own defence and described discovering the bodies of his wife and son at the dog kennels on their property known as Moselle.

Murdaugh admitted he stole and embezzled, and also lied about his drug habit, which his attorneys said cost $50,000 a week. But he said he would never lie about killing his family.

Murdaugh's attorneys argued that investigators had failed to pursue other possible suspects, including Murdaugh's drug suppliers and people angry over Paul's involvement in the February 2019 boating death of a teenage girl.

Waters, the prosecutor, called Murdaugh "a master liar" who stole money from a crippled client, from the family of a former Murdaugh maid who died in a fall years earlier, and from his law partners.

Waters focused on Murdaugh's lying to investigators on the evening of the crime that he had not been at the kennels before he discovered the bodies.

A video found on Paul's cell phone showed Murdaugh was there an estimated five minutes before the shootings.

"Everyone who thought they knew who he was, he's fooled them," said Waters. "He fooled Maggie and Paul too, and they paid with their lives."

Correction March 4, 2022: A previous version misstated that Murdaugh killed his daughter, rather than son.