DETROIT -- Davontae Sanford spent nine years in prison for four murder convictions that were later dismissed.

Now, he's filed a lawsuit against the city of Detroit, as well as two former investigators -- Homicide Unit Commander James Tolbert and Detective Sgt. Michael Russell -- who are accused of railroading Sanford into falsely admitting to crimes he never committed. Sanford, now 24, was an illiterate, learning-disabled 14-year-old at the time of his confession.

The 46-page lawsuit was filed Monday in Detroit federal court and claims Sanford walked out of his home early on Sept. 18, 2007, and asked Detroit police what was happening when they arrived to investigate a quadruple homicide on Runyon Street in Detroit that occurred the prior night.

Sanford was quickly identified as a possible suspect and taken in for "relentless" questioning that lasted two days, the lawsuit says. The lawsuit alleges Sanford was presented with a false confession written by Detroit police that contained details only known to the killers or investigators.

The purpose was to offer an authentic confession that would surely lead to the teen's conviction, attorneys claim.

Tolbert later testified that Sanford drew and signed a diagram of the murder scene, but years later confessed the diagram was actually drawn by police.

"The facts that have emerged since his wrongful conviction for these crimes have now proven that these officers ginned up evidence against Davontae, plain and simple," says a statement issued by the law firms representing Sanford in the lawsuit, Detroit-based Goodman Hurwitz & James and New York-based Neufeld, Scheck & Brustin. Detroit police "dictated a confession to him, typed it out, and then had Davontae sign the statements, even though he was unable to read."

Sanford, early in his trial, pleaded guilty to four counts of second-degree murders as part of an agreement to avoid a possible life prison sentence -- the mandatory sentence had be been convicted of first-degree murder. He received a sentence of between 39 and 40 years.

A week after Sanford's sentencing, a hit man named Vincent Smothers admitted he and an accomplice actually committed the Runyon Street killings. Smothers was ultimately convicted of eight other murders, but the Wayne County Prosecutor's Office never charged him with any crimes stemming from Runyon Street.

Despite Sanford being cleared more than a year ago, there is an ongoing state police investigation into the case.

Police "either deliberately failed to investigate details that incriminated Smothers and undermined Davontae's conviction, or did investigate such details and deliberately suppressed information that exculpated Davontae," the lawsuit says.

Sanford's appellate attorney sought a court ruling to overturn his conviction based on Smothers' admission.

"However, these efforts to prove Davontae's innocence were repeatedly stymied by continued misrepresentations by (Detroit police and Wayne County prosecutors), who continued to assert Davontae's guilt and fight his release in reliance on ... misrepresentations that Davontae had voluntarily confessed and voluntarily reported non-public information" about the murders, a statement issued by Sanford's attorneys on Tuesday said.

Wayne County Prosecutor Kym Worthy requested state police conduct another investigation in 2016. The findings included revelations that Tolbert potentially lied under oath about key evidence -- specifically, the diagram supposedly drawn by Sanford. Wayne County Circuit Judge Brian Sullivan vacated Sanford's 2008 sentence in June 2016.

Worthy hasn't indicated she believes Sanford was innocent -- in fact, she reiterated evidence that pointed toward his possible guilt in a 2016 statement -- but said she would no longer pursue charges against Sanford.

After leaving the Detroit Police Department, where he rose to the position of deputy chief, Tolbert worked as the police chief in Flint.

The lawsuit claims the Detroit Police Department was well aware of a pattern of unscrupulous behavior and alleged crimes committed by Tolbert, but chose to ignore them.

The incidents noted in the lawsuit include:

In 1999, the Southfield Police Department, investigated and found evidence that Tolbert had engaged in criminal domestic violence

In 2000, Tolbert was arrested for domestic assault. At the time of the incident and of his arrest, Tolbert was intoxicated while in possession of an open firearm

In 2005, Tolbert was accused by a Southfield police of a felony, filing a false police report

In 2006, Tolbert was arrested for domestic assault

In 2011, Tolbert was arrested and locked up for domestic assault

"Because of these actions by the Detroit Police Department, Davontae Sanford, an innocent child, spent the next almost 9 years in adult prison, often alone in solitary confinement, and there he lost his childhood in a living hell," Julie Hurwitz, one of Sanford's attorneys, said in a statement issued Tuesday.

Read the full lawsuit:

Davontae Sanford Lawsuit by Fergus Burns on Scribd