Lawyers representing Freddie Gray's family said Wednesday that they have accepted the Justice Department's decision not to charge any officers involved in his fatal ride in a Baltimore police van, but dangled a provocative new accusation: that members of the force "sabotaged" local prosecutors' murder investigation.

The lawyers, William H. Murphy and his son, Hassan Murphy, said they were skeptical when they first heard Tuesday that the Justice Department had concluded it could not prove the officers violated Gray's civil rights.

But the family lawyers said they met with DOJ lawyers and left understanding the case's shortcomings: the government's limited jurisdiction over deaths in police custody, and the relatively high burden of proof required to convict officers in such cases.

TOP: Baltimore Police Officer Garrett Miller, Sgt. Alicia White, Officer Edward Nero. BOTTOM: Baltimore Police Officer Caesar Goodson Jr., Lt. Brian Rice, Officer William Porter Baltimore Police

"We were surprised given what we know about the case," Hassan Murphy told reporters. "But after hearing what we heard, we are satisfied that this particular group of attorneys at the Department of Justice did what they were supposed to do in conducting this investigation."

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Related: Justice Dept. Won’t Charge Six Officers in Freddie Gray Death

He called the decision "a bitter pill for all of us to swallow," and said Gray's weary family ─ who received a $6.4 million settlement from the city in 2015 ─ "will have a chance now to really heal and be with themselves."

But the elder lawyer said that the case may still produce new revelations about Baltimore State's Attorney Marilyn Mosby's unsuccessful attempt to convict the six officers on charges of murder or manslaughter.

"In the future, hopefully before this next election, you will see the extent to which various members of the police department of Baltimore city deliberately obstructed this investigation," William H. "Billy' Murphy said. "Because of my unique role, I have been legally made privy to documents I believe, once they are able to be released to the public, will show without question that in several significant ways her investigation was sabotaged."

Freddie Gray NBC

The police department declined to comment.

Gray, 25, died of spinal cord injuries on April 19, 2015, five days after his arrest following a foot chase with police that resulted in a summons for possession of a switchblade knife. He was put in a police van shackled but not restrained by a seat belt, and suffered his fatal injuries sometime during the ride.

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Gray's death set off public unrest, including rioting and looting that in turn triggered two investigations by the Justice Department: one civil, one criminal. The civil probe found a pattern of unconstitutional stops, searches and arrests of black residents, and the use of unnecessary force against them. The city agreed to make sweeping changes to its police department in order to avoid a federal lawsuit.

The criminal probe focused on six members of the department: Officers Caesar R. Goodson Jr., Garrett E. Miller, Edward M. Nero and William G. Porter; Lt. Brian W. Rice and Sgt. Alicia D. White.

All six escaped murder or manslaughter charges in state courts last year. Three were acquitted at trial and another case ended in a mistrial before Baltimore States Attorney Marilyn Mosby dropped all remaining charges.

Tuesday's decision by the Justice Department effectively ended all criminal cases against the officers. But several of them still face disciplinary charges that could end their careers.