Jeffs has refused to answer any questions in previous depositions, the lawyers wrote. Private investigator Sam Brower, who sat in on two depositions with Jeffs, confirmed this to KUER-FM.
“To every question posed to him, he pleaded the Fifth Amendment. He didn’t answer a single question,” Brower said.
R.H.'s lawyers argued in a July 15 filing that this isn't a legally valid reason to not depose Jeffs, KUTV-TV reported.
"Ironically, Defendants assert that Warren Jeffs has had a mental breakdown, yet provide the court with no evidence or factual support for such assertion. Any such objection can be made by Warren Jeffs, not the UEP Trust," R.H.'s lawyers wrote.
This isn't the first time Jeffs' mental or physical health has been called into question.
Jeffs, 63, is serving a life sentence in Texas after being convicted in 2011 of sexually assaulting girls he considered brides, CBS News reported.
He tried to hang himself in 2007 in a Utah jail and in 2009 had to be force-fed at an Arizona jail. In 2011, he was put in a medically induced coma after fasting in the Texas prison.
Jeffs has a court date scheduled for Aug. 27 in St. George, Utah, to determine whether he will be ordered to testify.