JACKSON -- A Greenwood oncologist is suing Attorney General Jim Hood and officials of the Mississippi Department of Mental Health, claiming they're illegally confining him to cover up how an alleged hit man died in April 2012.

The suit was filed Tuesday in U.S. District Court in Jackson on behalf of Dr. Arnold Smith by his wife, Mary Smith. The oncologist has been confined at the Mississippi State Hospital in Whitfield since 2014, after a judge ruled him mentally incompetent for trial on capital murder and conspiracy to commit murder charges.

"Defendant Hood has a personal financial motive and a personal liberty motive to unlawfully use multiple attorneys and resources from the attorney general's office and the Mississippi Department of Mental Health during Dr. Smith's civil commitment case to wrongly and unlawfully seek the continuing vilification and incarceration of Dr. Smith," the suit states.

Hood spokeswoman Rachael Ring noted Smith still faces criminal charges in the incident and has at least two other federal lawsuits since his 2012 arrest.

"This baseless suit is the most recent in a series of failed attempts by Smith to sue state officials," Ring wrote in an email. "We are confident that this suit will be dismissed."

Authorities have said Smith hired Keira Byrd to kill attorney Lee Abraham, with whom Smith had disputes dating back to Abraham's representation of Smith's prior wife in a divorce case. Byrd died in a shootout at Abraham's office in April 2012, and the suit claims Larry Ware, an investigator for Hood, killed Byrd "execution-style" and not in self-defense, as Hood has said happened.

"The best evidence shows that Keaira Byrd was killed with an execution-style shot to the top of the head after Mr. Byrd was already down," the suit alleges, citing a crime-scene reconstruction that includes an illustration of one man standing over a second man on the ground and shooting him. The suit says Byrd never fired a shot on entering the office, where Abraham, Ware and a second investigator were present. A third attorney general's investigator was stationed outside. Byrd was accompanied by Derrick Lacy, who has yet to be brought to trial on his own charges of capital murder and conspiracy to commit murder charges. A third man, Cordarious Robinson, faces conspiracy charges, with authorities alleging he helped connect Smith to Byrd.

Smith argues that his constitutional rights, due process and equal protection rights are being violated by the way he's being held, saying that his 2014 indefinite involuntary commitment and the following renewals are also illegal under state law. The suit says the Department of Mental Health illegally put Smith in the criminal wing of the hospital, failed to conduct an evaluation within three months of commitment and then conducted an evaluation in May 2015 that was a "farce."

The suit claims that lawyers Ralph Chapman, Lee Abraham, Scot Spragins and Lawrence "Lucky" Tucker tried in August 2014 in a "baseless and illegal scheme" to try to force Mary Smith to pay "millions" to Abraham to settle various civil claims.