(NewsNation) — Alex Murdaugh’s brother, John Marvin Murdaugh, was the last defense witness. He testified that state agents told him they had a shirt covered in blood that proved his brother was the killer.

That evidence has not been presented at trial, although Alex Murdaugh’s lawyers said in pretrial motions that a state agent claimed to find blood. Later tests disproved the assertion and testing destroyed the garment before the defense could see it.

State agents released the crime scene less than 12 hours after the killings, John Marvin Murdaugh said. When he went to look around that morning, he saw blood, brains and a piece of Paul Murdaugh’s skull. He said he felt compelled to clean.

“No mother or father or aunt or uncle should ever have to see or do what I had that day,” he said.

He also spoke to his dead nephew that day, telling the court: “In my mind and out loud I told Paul I loved him. I promised him I’d find out who did this to him.”

“Have you found out?” defense attorney Jim Griffin asked.

“I have not,” he replied.

Lena Sisco, a body language expert, said John Marvin Murdaugh’s emotions looked “very real.”

“When people fake emotion, you can tell and when it’s real, you can tell. That emotion looks very real to me,” Sisco said on “Morning in America.” “Just listening to the words that he’s saying and matching that up to the emotion that I see, it all sounds very plausible, and what he’s preaching and saying on the stand.”

Meanwhile, Sisco said Alex Murdaugh “was frozen” as he listened to his brother’s testimony. She also noted that he was “balled up,” which is a position people sometimes go into when they’re nervous, but it could also mean “a bunch of things.”

“We can’t jump the gun and say, oh, automatically, he’s covering up, so you must be lying. When we’re experiencing something traumatic, we will go internal, and we become smaller, the chin tucks the shoulders curl in, and it’s almost as though we’re closing off the whole outside,” Sisco explained.

She added: “The emotion right now as he’s balling up and closing, could be actual genuine emotion because of listening to the stress of his brother talk about these murders. And if he did, in fact, kill his wife and his son, then this makes complete sense.”

Sisco also said throughout the trial, Alex Murdaugh’s “words tell me way more than his body language.” She said she’s analyzed hundreds of 911 calls and she always pays close attention to the first few words.

In Alex Murdaugh’s 911 call, Sisco said “his first few words were I need the police and an ambulance.”

“So that tells me, OK, if you’re focusing on the police, that means you’re thinking crime. That means you’re thinking this is an investigation, not hey, I gotta help my son and my wife because they just got shot and they could be dead,” Sisco explained. “So that tells me a lot about what where the brain is going and what they’re thinking about and what he’s most concerned about.”