(CNN) -- Former New England Patriots star Aaron Hernandez used "coded messages" in jailhouse calls to discuss the killing of Odin Lloyd, Massachusetts prosecutors said in court papers.
Hernandez, 24, is being held on first-degree murder and weapons charges in the shooting death last year of his friend Lloyd. Hernandez has pleaded not guilty.
In court papers filed Thursday, the Bristol County District Attorney's Office asked a state court to order the Sheriff's Office to turn over recordings of jailhouse calls and records of the people who visited Hernandez since the former tight end was arrested in Lloyd's killing in June.
Prosecutors said Hernandez used coded messages when discussing with friends allegations that he planned the June 17 killing of Lloyd in a North Attleborough, Massachusetts, industrial park, where Lloyd was found shot to death.
Hernandez's lawyers moved to quash the request, calling it a "fishing expedition."
"There is absolutely no basis to provide the Commonwealth with access to all of the defendant's recorded phone calls, past, present, and future," his attorneys, Michael Fee and Jamie Sultan, said in their court filing.
Those who have visited Hernandez included his fiancee, Shayanna Jenkins, and cousin, Tanya Cummings Singleton, both of whom face charges in connection with the Lloyd homicide, the court papers said.
"Both of these co-defendants have been charged as accessories in the underlying offense of murder on the theory that they provided assistance to the defendant after the commission of that offense," Bristol Assistant District Attorney Roger L. Michel Jr. wrote in a court papers requesting the tapes and records.
Michel wrote that in jailhouse phone conversations Hernandez discussed "matters directly relevant to the circumstances surrounding the murder of Odin Lloyd; viz: the defendant's subjective belief about his criminal liability; his use of coded messages to communicate with persons outside of jail; related prior offenses; inculpatory denials of ownership of a vehicle connected with the investigation; the extent of his control over persons charged as accessories; other matters relating to his codefendants, including their whereabouts and likely criminal liability.''
Both detainees and people they call are warned by the jail that their conversations are recorded.
Authorities have said that Hernandez and two other men picked Lloyd up from his Boston apartment in a rental car shortly before he was found shot to death June 17.
Surveillance cameras then captured the rental car leaving the crime scene and Hernandez carrying a gun as he returned to his home minutes later.