MANILA, Philippines - A man claiming to be one of several triggermen in the November 23 Maguindanao massacre could be the first state witness to admit actually participating in the crime, a lawyer said Wednesday.

Lawyer Harry Roque, who is representing 13 women who were widowed in the massacre, said government prosecutors have yet to decide whether to accept the testimony of "Jessie", an alleged gunman of the Ampatuan family.

"[Jessie] has yet to be accepted in the witness protection protection. This is the first time that a gunman is offering to testify in the case," Roque said in a radio dzMM interview.

He added that one potential witness, a policeman, had filed an affidavit, saying that he was involved in the massacre. The policeman, however, later recanted.

At least 57 people were killed in the massacre, which is considered the worst case of election-related violence in the country's history. Close to 200 people have been implicated in the murders including Datu Unsay Mayor Andal Ampatuan Jr.

In a Philippine Star report, Jessie said he was one of 7 gunmen who used high-powered firearms to kill the massacre victims in a hilly portion of Sitio Masalay, Barangay Salman. He said the 7 included himself, Ampatuan Jr., Datu Kanor, Datu Ban, Datu Mama, a certain Kudja, and a police officer whom he knew to be Police Officer 1 Ando Masukat.

Jessie said it was Ampatuan Jr. himself who shot Genalyn Mangudadatu, wife of his rival Toto Mangudadatu, using a baby M203 rifle grenade launcher. He said that after the massacre, Ampatuan Jr. called up his father, Andal Sr., to send a backhoe so they could bury the bodies.

Jessie earlier told Al Jazeera that Ampatuan Jr. had ordered the murders of several witnesses in the massacre. He said he left an Ampatuan safehouse last January after the mayor placed a $45,000 bounty on his head.

Roque, meanwhile, said he is set to file a case before the National Police Commission, asking for the immediate removal of all police officers who participated in the massacre.

He said he will also file a motion to allow his clients to present evidence in the civil aspect of the case.