A Baton Rouge man suspected of killing three homeless people in December "did not know right from wrong" when he allegedly shot one of them to death at a vacant house, his attorney claims.

Jeremy Anderson, 29, who pleaded not guilty in March to a first-degree murder charge in the slaying of Tony Williams, now intends to enter dual pleas of not guilty and not guilty by reason of insanity, East Baton Rouge Parish Assistant Public Defender Carson Marcantel said.

Marcantel also wants state District Judge Tarvald Smith to appoint doctors to assess Anderson's mental competency at the time of Williams' killing and his current ability to assist his lawyer in preparing his defense.

Marcantel indicated in his filings that he met with Anderson for an extended period of time after his March arraignment and also reviewed his medical records, and now believes his client "did not know right from wrong on the date of the alleged offense."

Marcantel said in documents filed last week that he does not believe Anderson can currently assist him in the preparation of his defense.

East Baton Rouge Parish District Attorney Hillar Moore III said Monday his office welcomes a "thorough mental health evaluation" and looks forward to moving the case forward.

Moore had said previously that his office will prosecute Anderson as an alleged serial killer and introduce evidence of the Dec. 13 killing of Christina Fowler and Gregory Corcoran at his trial in the slaying of Williams.

Moore has not indicated whether his office will pursue the death penalty. If it does not, Anderson would be sentenced to life in prison if found guilty of first-degree murder.

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Williams, 50, was found shot to death Dec. 27 on the front porch of a vacant home on 18th Street near Convention Street. That home is a few hundred feet from Anderson's home.

Anderson was arrested in early January in the slaying of Williams and in the killing of Fowler, 53, and Corcoran, 40, who were found dead beneath the North Boulevard overpass. Fowler and Corcoran were huddled in blankets beside an empty shopping cart less than a block from Anderson's home on South 17th Street.

All three victims were shot in the head.

Anderson was arrested after officers received information from someone who heard him confess to the killing of Williams, Baton Rouge Police Chief Murphy Paul has said. Detectives executed a search warrant at Anderson's home and seized evidence linking him to the crimes, Paul said.

When officers questioned Anderson he made "incriminating statements" that placed him at the crime scene," the chief said. Anderson, while giving a statement to detectives, confessed to killing Fowler and Corcoran, an arrest report says.

Williams, Fowler and Corcoran were killed in an area where many of Baton Rouge's homeless residents congregate because of its proximity to several shelters and other service providers.

Police don't have a motive for the slayings, and it's not known whether the victims were killed at random or specifically targeted — either for being homeless or for some other reason. Police said they weren't sure whether Anderson knew the victims.

Anderson's criminal history in East Baton Rouge leading up to the killings included two misdemeanor convictions: one for illegal carrying of weapons in 2013 after officers found him with a stolen gun, and the other for simple battery in 2014 after his arrest on domestic abuse counts.

Email Joe Gyan Jr. at jgyan@theadvocate.com.