Lead prosecutor Creighton Waters asked Crosby, who arrived at the crime scene the night of the murders to support his grieving friend, what Murdaugh told him.
"My understanding of what he told me was that he checked them before he called 911," Crosby replied.
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The disbarred attorney's account allegedly changed after data from his Chevrolet Suburban revealed he called police less than 20 seconds after his car pulled up at the murder scene.
Murdaugh has denied fatally shooting his wife and son near the dog kennels at the family's sprawling hunting estate known as Moselle at about 8:50 p.m.
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Waters also asked Crosby when he had first heard Murdaugh admit that he was at the crime scene with the victims minutes before they were murdered.
Crosby replied that it was during Murdaugh's testimony last week.
Murdaugh initially told Crosby and investigators that he had not gone to the kennels the night of the slayings, but he changed his story after video recovered from Paul's phone in 2022 contradicted that claim and placed him at the dog kennels at 8:45 p.m.
On cross-examination, defense lawyer Dick Harpootlian suggested that Crosby's testimony was informed by his resentment of Murdaugh for stealing from the law firm where they were once partners.
"Are you angry at him for stealing your money?" Harpootlian asked several times.
"I have had anger with him, extreme anger, Mr. Harpootlian, because of what he did to my law firm, my partners, my clients, his clients, our clients, what he did to his family, what he's did to so many people" he replied.
However, Crosby insisted Murdaugh's betrayal had no impact on his testimony.
Prosecutors recalled Dr. Ellen Riemer, a pathologist who previously testified that the second shot that killed Paul grazed his shoulder, entered his neck and blew his brain out the top of his head.
A pair of defense witnesses Monday testified that Paul was shot in the back of the head by a shotgun pressed against his skull, and the shooter would have been covered in Paul's blood, brain matter and tissue.
However, Reimer held firm on her initial conclusion that this was not a contact injury.
"His eyes would have been displaced from the orbital bone," she said of the damage from a contact wound. "His entire face would have been split open."
Paul's brain was severed from his body and found near his feet, but his face remained intact, according to prior testimony.
The defense, which launched its case last week, called 14 witnesses – including Murdaugh himself.
The defendant's brother, John Marvin Murdaugh, was the final defense witness Monday. He wept as he told jurors that he cleaned up what remained of his slain nephew's remains inside the feed room.
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"I saw blood, I saw brains, I saw pieces of skull," he said, choking back tears. "It was terrible."
He said he was stunned that investigators had left the mess behind.
"It's the hardest thing I've ever been through in my life," he testified.
In that difficult moment, he said, he made a vow to his nephew. "I told Paul I loved him, and I promised him I'd find out who did this," he said.
Waters said Tuesday that he planned to call a total of seven reply witnesses.
At the end of the rebuttal case, jurors will take a field trip to the crime scene. Closing statements could begin as early as Wednesday.
Prosecutors have argued that Murdaugh used a shotgun to blow off his son's head and a rifle to execute his wife to distract from his financial malfeasance.
The trial has chronicled Murdaugh's stunning downfall from the wealthy scion of a powerful legal dynasty to an admitted drug addict and thief who allegedly swindled his law firm and clients out of nearly $9 million.