The suspect in an alleged September assassination attempt against then-presidential candidate Donald Trump has asked a judge to suppress eyewitness testimony.In a new court filing, Ryan Routh and his lawyers said the statements given by eyewitness "T.C.M." should be thrown out as the witness "identified Mr. Routh as the perpetrator through impermissibly suggestive means." Routh has pleaded not guilty.Newsweek has contacted Routh's legal team and the FBI for comment via email.Why It MattersRouth's lawyers have said the "substantial likelihood of misidentification" due to the FBI's "improper photographic procedure" violates Routh's right to due process, making their argument a Fifth Amendment claim.What To KnowOn September 15, T.C.M. reportedly heard gunshots coming from the Trump International Golf Club in Palm Beach.The witness told police he then saw a disheveled white male, who was 6-foot-2 with light-colored hair, wearing a dark shirt and dark pants.The filing, citing a detective from the Palm Beach County Sheriff's Office, said T.C.M. described the man "as a younger male in his twenties."In the court document, Routh's legal team said that although T.C.M. heard gunshots and saw someone fleeing the golf course, his description of the suspect did not match Routh.The lawyers added that the police showed T.C.M only one photograph of Routh to identify him, which they suggested was improper photographic procedure.The witness also said he saw the man drop a small dark object through the sunroof of a black vehicle, which T.C.M. took three photographs of. He wrote down the license plate of the car as 97 EEE.One hour later, and 40 miles north of Palm Beach, Routh, who was 58 years old at the time, was pulled over by Martin County deputy sheriffs in a car with the license plate 97EEED. His car did not have a sunroof.Police shut down the highway with patrol cars and helicopters, and officers arrested Routh.According to the filing, Routh was the only suspect photographed by the police, meaning T.C.M. received one image to identify, as opposed to picking someone from a lineup.Routh's lawyers have said the presentation of Routh in handcuffs surrounded by law enforcement was "impermissibly suggestive," arguing that the urgency of the situation involving a presidential candidate and the use of state and federal agencies "created a heightened pressure to make the identification."They added that the use of a single photograph to identify the suspect meant the "FBI also led T.C.M. to believe that Mr. Routh was the one, and only, suspect.""These repeated, suggestive procedures created a substantial likelihood of misidentification, for which the introduction would violate Mr. Routh's right to Due Process," the lawyers wrote.While the witness said he heard gunshots and Palm Beach County Sheriff Ric Bradshaw said an AK-47-style rifle with a scope, a GoPro camera and two backpacks containing ceramic tiles were found in the bushes at the golf course, the Secret Service later confirmed that no shots were fired by the suspect as he did not have a line of sight to Trump.According to the court filing, when Routh was first taken into custody, T.C.M. also saw him in person. The filing cited a detective's report that said: "Upon seeing the detained person, [T.C.M.] notices that the person had the same hair and build. [T.C.M.] asked to see the side profile of the person and identified him as the person he saw running from the bushes along the south side of the Trump National Golf Course."What People Are SayingRouth's lawyers wrote in their motion to suppress the testimony: "Indeed, there are significant discrepancies between T.C.M.'s description and Mr. Routh's actual appearance. T.C.M. described the suspect as a younger male in his twenties, whereas Mr. Routh is 58 years old, almost four decades older. Mr. Routh's clothing and the vehicle's lack of sunroof also did not match T.C.M.'s description."Yet local law enforcement and the FBI unnecessarily suggested that the detained man arrested on the highway and the single man in the photograph was the assailant. These were not reliable positive identifications. All of these circumstances give rise to a substantial likelihood of irreparable misidentification. Therefore, the out-of-court identifications should be suppressed."What Happens NextRouth's trial is scheduled to begin on September 8. The defense has argued that the testimony from T.C.M. would be "constitutionally inadmissible" in court.