A US federal judge has thrown out a lawsuit by Alex Murdaugh seeking $600,000 in legal fees from the former court clerk whose misconduct led to his murder convictions being overturned on appeal.

Murdaugh sued Becky Hill in May, saying she violated his right to a fair trial over the deaths of his wife and son. A jury found Murdaugh guilty, but the state supreme court overturned the convictions and life sentences earlier this year, saying Hill's comments to jurors suggested the once-prominent lawyer was guilty and his testimony in his own defense could not be trusted.

The problem with Murdaugh's legal reasoning is he would have had to spend the money anyway, because it was not Hill who investigated or pursued justice against him, Judge Richard Gergel wrote in his ruling on Wednesday. "Plaintiff's claim contains a fatal flaw – the lack of a causal connection between the funds he expended for his defense in the first trial and defendant's misconduct. Defendant had no role in the initiation of criminal charges against plaintiff," Gergel wrote.

Murdaugh said in court papers he spent $600,000 from a retirement account to pay for his lawyers in his first trial and will need more money to pay them for his retrial next year in the case that has become a true crime sensation with a streaming miniseries, bestselling books and dozens of podcasts.

Even with his murder convictions overturned, Murdaugh remains in prison. He pleaded guilty to stealing about $12 million from his clients and is serving a 40-year federal sentence at the same time as a 27-year state sentence for his financial crimes. His retrial on the murder charges has been scheduled for April.

Investigators said Murdaugh was addicted to opioids and his complex schemes to steal money from clients and his family's law firm were starting to unravel so he killed his wife and son to divert attention and buy time to find a way out of his problems.