Many were surprised that Arthur would consider a deal.
Arthur and his son, Perry were both charged with conspiracy to murder Janet's parent's, Perry's former in-laws, Lawrence and Carolyn Levine.
Perry is also charged with killing his wife Janet nine years ago.
Monday, Arthur told magistrate Cliff Knowles he'd waive his right to be indicted on the murder conspiracy charge.
That cleared the way for him to go before federal Judge Todd Campbell. March pleaded guilty to one count of solicitation across state lines to commit murder.
"We're very close to making a resolution in this case. We are very happy about that. I think that my client looks better than he has looked previously in appearances because I think it's relieved a great a deal of anxiety and stress for him knowing what the ultimate outcome will be," said Fletcher Long, Arthur's Attorney.
In the deal, Arthur will do 18 months in a federal medical facility. In return, he will help the prosecution with the two criminal cases against Perry.
Many now wonder with Arthur cutting a deal if Perry March will be next.
There have been negotiations and sources tells NewsChannel 5 one deal calls for Perry March to served 23 years in exchange for a guilty plea.
Arthur was never charged in the murder case but, he will share what he knows about Janet's murder.
He has already taken Metro detectives to a rural area outside Bowling Green, Ky. Sources said Arthur told detectives he and Perry disposed of Janet's body under a brush pile that was later burned.
Monday, the assistant U.S. attorney said Arthur March revealed more details about the death of Janet March.
Arthur March said Perry confided in him, and that Perry killed his wife during an argument at their Forrest Hills home. Arthur said Perry used a wrench as the weapon. He apparently beat Janet in the head.
Perry March does continue to maintain his innocence.
Arthur March will now remain in federal custody.
Officials said detectives would return to Kentucky to search for Janet March's remains after nearly 10 years, and regardless of the conditions of the remains, state forensic official Michael Tabor is prepared to identify them.
"Depending upon the condition of the teeth and the number of teeth that have been recovered that would help speed up or slow down the identification process," said Tabor.
Tabor has all of Janet's dental records. He's said it will be easy to identify her because of her silver fillings.These new details bolster the state's case against Perry March. And investigators say, it sends a strong message.
"The message is, we will always work every day, to solve every possible case we can," said metro Police Chief Ronal Serpas.
Arthur March's attorney said his client's plea agreement is proof he is sorry for what happened.
"A lot of people get all hung up in the words 'well, has he apologized?' Actions speak louder than words. Don't say you're sorry. Act sorry. I would submit to you that Arthur March's actions are certainly indicative of his being sorry and trying to make some sort of reparation," said Long.
Arthur said Perry confessed to hitting Janet with a wrench because she threatened him with a knife. He also said Perry temporarily hid Janet's body at a construction site near the March's home before they allegedly disposed of the body in Kentucky.
Monday's legal developments surrounded the federal case of conspiracy to murder the Levines. But state investigators say this federal plea deal will, no doubt, help a great deal with their murder case against Perry March.
"I think Arthur March is guilty of loving his son," said Long.