A woman arrested in the death of a Canadian legal scholar in Florida has been charged with first-degree murder for her alleged role in what investigators have suggested was a murder-for-hire rooted in a bitter divorce.

A U.S. grand jury indicted Katherine Magbanua this week in the 2014 killing of Dan Markel, a law professor at Florida State University who was born in Toronto.

Magbanua -- the third person arrested in the case -- was initially taken into custody and charged with second-degree murder in October.

That month, one of the two others arrested in the case, Luis Rivera, suddenly pleaded guilty to second-degree murder. He told investigators he and his co-accused, Sigfredo Garcia, were paid to kill Markel because the academic's ex-wife allegedly wanted full custody of their two children.

Markel's ex wife, Wendi Adelson, and her family have denied any involvement in the professor's death and she has not been charged. Her brother has come under police suspicion but is also not charged.

Police have said Magbanua was in a relationship with Adelson's brother and was the only link between Markel's ex-wife's family and the two men arrested in the professor's death.

Assistant State Attorney Georgia Cappleman said this week it was possible Magbanua could help lead authorities to other arrests in the case, but noted that depended on the woman's co-operation.

"If she co-operated and was willing to testify truthfully against other involved parties that could have an impact on additional arrests/prosecutions," Cappleman told The Canadian Press. "So far there is no indication that she intends to co-operate."

Markel was gunned down in his Tallahassee, Fla., garage in July 2014.

Court documents have indicated he and his ex-wife fought over Adelson's push to move her two small children to South Florida to be closer to her family.

At the time of Markel's death, the two were battling over money, with Adelson contending that Markel did not pay her as much as he was supposed to under their divorce agreement. Markel also complained that his mother-in-law was disparaging him and wanted the court to prohibit her from having unsupervised visits with his children, court documents have shown.

Police have alleged the hit on Markel was arranged by Magbanua, who had been romantically involved with both Garcia -- with whom she has two children -- and Markel's brother-in-law.

Rivera has told investigators Garcia allegedly asked him to help in the plot. He also alleged Magbanua divided up payment for the hit.

Investigators say in the weeks leading up to Markel's killing and immediately thereafter, there were hundreds of calls between Markel's brother-in-law, Charlie Adelson, and Magbanua, and between Magbanua and Garcia, often moments apart.

Police documents also allege that shortly after the killing, Garcia bought two cars and a motorcycle and Rivera bought a motorcycle. They further allege that Magbanua received cheques from a dental practice run by Charlie Adelson and his parents, though she allegedly never worked there.

-- With files from The Associated Press