John Marvin Murdaugh, the younger brother of Alex Murdaugh, wipes a tear while giving his testimony during the double murder trial (Picture: AP)

The brother of a disgraced lawyer accused of murdering his wife and younger son tearfully recounted cleaning up his nephew’s remains at the crime scene.

John Marvin Murdaugh testified as the final witness in defense of his older brother, disbarred lawyer Alex Murdaugh, who has pleaded not guilty in the killings of his wife Maggie, 52, and son Paul, 22.

In the Walterboro, South Carolina, courtroom on Monday, John cried as he told jurors that cleaning Paul’s remains was ‘the hardest thing’ he ever did.

‘I saw blood, I saw brains, I saw pieces of skull,’ said John. ‘It was terrible.’

John Marvin Murdaugh (right) walks to the witness stand past his brother, Alex Murdaugh (left), and defense attorney Dick Harpootlian (center) during Alex Murdaugh’s double murder trial at the Colleton County Courthouse (Picture: AP)

John went to the dog kennels at the crime scene at Alex’s hunting estate and found Paul’s remains across the feeding room. John said he felt he needed to collect the remains of Paul, who had worked at his equipment shop.

‘It felt like it was the right thing to do. I felt like I owed him, and I started cleaning, and I promise you no mother or father or aunt or uncle should ever have to see or do what I did that day,’ John said. ‘It’s the hardest thing I’ve ever been through in my life.’

John said he made a promise to Paul as he cleaned up.

‘I told Paul I loved him, and I promised him I’d find out who did this,’ John said.

Alex Murdaugh cries during his double murder trial at the Colleton County Courthouse in Walterboro, South Carolina, on Monday (Picture: AP)

When asked by defense lawyer Jim Griffin if he discovered who the killer was, John said: ‘I have not.’

Investigators had told John and his siblings that they knew Alex was responsible for the double murder because of the T-shirt he wore.

‘They told us that it was covered in blood,’ testified John. ‘They went so far as to tell me on the police bodycam that he takes his shirt and wipes his face and that’s how they knew that Alex was at the scene, and that he was the one.’

According to the defense team, the T-shirt didn’t test positive for blood.

Alex Murdaugh is escorted into the courtroom at the Colleton County Courthouse before the start of his double murder trial on Monday (Picture: AP)

An expert said that Alex’s shirt was ‘stained with high-velocity blood spatter resulting from shooting Maggie and Paul’, but prosecutors did not end up presenting evidence to back up the claim.

The defense wrapped up its case after calling 14 witnesses over two weeks. Monday also marked the sixth week of Alex’s trial. Among the defense’s witnesses was Alex’s surviving son Buster, 26, who wept as he recalled his dad calling him to say Maggie and Paul were dead.

Alex has plead not guilty to two counts of murder and two weapons charges.

Judge Clifton Newman ruled that jurors will be allowed to visit the Murdaugh family’s estate where the two bodies were found after the rebuttal witnesses, and before closing arguments.

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Disbarred lawyer Alex Murdaugh’s defense team called his brother John Marvin Murdaugh as their final witness in the double murder trial.