Attorneys for suspected serial murderer Jeffery Lee Guillory have subpoenaed convicted serial killer Sean Vincent Gillis to testify at Guillory’s upcoming trial and have requested Gillis’ taped police interviews and interrogations, one of Guillory’s attorneys said Wednesday.

Whether Gillis actually takes the witness stand at Guillory’s second-degree murder trial, set for Sept. 19, remains to be seen because the defense cannot call Gillis to the stand if all he intends to do is assert his Fifth Amendment protection against self-incrimination.

Guillory’s defense team contends Gillis associated with Renee Newman, the 46-year-old Baton Rouge woman Guillory is accused of killing in 2002.

State District Judge Tony Marabella said Wednesday he will make a determination Sept. 13 regarding Gillis’ “status as a witness in this case.’’

“Mr. Gillis needs to decide what he wants to do. If he pleads the Fifth, the question is why,’’ Franz Borghardt, one of Guillory’s court-appointed attorneys, said after a hearing in the case.

Authorities have alleged that Guillory and Gillis targeted women who led high-risk lifestyles.

Guillory, 45, was arrested in late 2009 in the slayings of Florida Edwards, Sylvia Cobb and Newman, all of Baton Rouge. The bodies of Edwards and Cobb, both 36, and Newman were found in 1999, 2001 and 2002, respectively.

Guillory was indicted in Newman’s killing in May 2010.

A Baton Rouge police detective testified at a hearing in Guillory’s case last fall that Newman — who was strangled — reportedly associated with Gillis.

“We’re going to put on a defense,’’ Borghardt pledged Wednesday. “We believe we can independently show there was a relationship between Mr. Gillis and Ms. Newman.’’

Prosecutor Dana Cummings told reporters there is nothing in Gillis’ statements to police that hurts the state’s case against Guillory.

“We’re very confident about our case, even if part of the statement is suppressed,’’ she said.

Borghardt said the defense is seeking to have part of Guillory’s five-hour statement thrown out, arguing that Guillory was questioned even after asking for a lawyer.

“We believe he invoked it (his right to counsel) at least twice,’’ Borghardt said.

A DNA analyst with the Louisiana State Police Crime Lab also testified last fall that there is only a 1-in-9.76 quadrillion chance that DNA found on the bodies of Newman and Edwards belongs to someone other than Guillory.

Guillory remains a suspect in several other unsolved killings of women in Baton Rouge that occurred in the late 1990s and early 2000s, authorities have said.

Gillis was convicted in 2008 of first-degree murder in the 2004 strangulation and mutilation of Donna Bennett Johnston, of Baton Rouge. He was sentenced to life in prison after the jury deadlocked during the penalty phase.

Gillis also pleaded guilty to second-degree murder in 2007 and was sentenced to life in the 1999 killing in Port Allen of Joyce Williams, of Baton Rouge.

Authorities have said Gillis confessed to killing eight south Louisiana women between 1994 and 2004.