Attorney Jim Elliott, who represents the Lowndes County Sheriff's Office, called the allegations "false, outrageous, scurrilous and scandalous."
The claims were made Friday in an amendment to a $100 million wrongful death lawsuit filed in January.
It's the second revision in a week in response to a judge's order to specify claims.
A revision made earlier in the week accused Prine, Taylor and a local FBI agent of placing Johnson's body into the mat themselves.
The Johnsons' attorney, Chevene King, seemingly backed off those earlier claims after receiving a letter from Elliott on Wednesday demanding the lawsuit be dropped within 30 days under Georgia's abusive litigation statute.
"The Johnsons and their lawyer have been repeatedly asked to identify witnesses or other evidence that support their claims. In over two and one-half years, the Johnsons and their lawyer have never identified a single witness or a shred of evidence to support any of what they say or claim," Elliott told CNN in a written statement.
Attorney Warren Turner, who represents Lowndes County Schools, told CNN he planned to send a similar letter to King.
"Seven months after filing suit and 31 months after Johnson's accidental death, no witness has ever been identified, nor any evidence offered to support such new claims. It is irresponsible, and just plain wrong," attorney Warren Turner said on behalf of Lowndes County Schools.
An attorney representing the FBI agent did not immediately return CNN's call for comment.
In May 2013, the Georgia Bureau of Investigation released its autopsy report, which determined the cause of Johnson's death was accidental positional asphyxia. The case was closed.
The following month, Johnson's body was exhumed. Johnson's parents hired Florida-based forensic pathologist Dr. William Anderson, who found evidence
of "unexplained, apparent non-accidental blunt force trauma" to Johnson's neck. Anderson determined Johnson's death was the result of a homicide.
U.S. Attorney Michael Moore launched a federal investigation
into the death of Kendrick Johnson in October 2013.
An attorney for the FBI agent and his family confirmed to CNN in December 2014 that the agent and one of his sons, who had been a schoolmate of Johnson's, received letters confirming that they were the targets of the federal investigation.
In July, U.S. marshals seized cell phones, computers and other items from the homes of the agent and the former schoolmate.
The federal investigation is ongoing.