BALTIMORE Defense attorneys are seeking a new trial for a man convicted in the high-profile slaying of Phylicia Barnes, the Monroe teenager who disappeared in Baltimore two years ago.

Michael Johnson was convicted this month of second-degree murder in the death of 16-year-old Phylicia Barnes, an honor student who disappeared while visiting relatives in Baltimore in December 2010. Her body was found four months later in the Susquehanna River.

Johnson’s lawyers filed a motion for a new trial on Tuesday. Attorney Russell Neverdon says prosecutors improperly tried to bolster the credibility of a witness who testified that Johnson asked him for help disposing of Barnes’ body.

Baltimore State’s Attorney Gregg Bernstein says the state will respond to the motion at the appropriate time.

Johnson’s sentencing is scheduled for March 20. He faces up to 30 years in prison.

The disappearance of Phylicia Barnes, an honor student from Union Academy in Monroe, in December 2010 captured national attention. Police called it the “Baltimore Natalie Holloway case,” a reference to the white Alabama high school student who caused a media sensation when she disappeared during a school graduation trip to Aruba.

Barnes was scheduled to graduate a year early. She had “a stack of acceptance letters” to college, according to prosecutors. She planned to attend college at Towson University, just north of Baltimore.

A jury of six men and six women deliberated Johnson’s fate over the course of three days before finding him not guilty of the more serious charge of first-degree murder but convicting him of second-degree murder.

The verdict capped more than a week of salacious trial developments that included more than 30 witnesses and a 16-minute sex video showing Phylicia, her half-sister, Johnson and another man naked and kissing. Her older half-sister, Deena Barnes, who dated Johnson for 10 years, tearfully admitted allowing her to drink alcohol, smoke marijuana and sleep in rooms with boys.

Prosecutors called to the stand a convicted criminal named James McCray – defense attorneys called him a “professional snitch” – who said he saw Phylicia’s body and told Johnson how to dispose of the corpse without leaving any physical evidence.

The Baltimore Sun reported that defense lawyers accuse prosecutors of withholding information about McCray being held in Baltimore County on felony charges that were dropped “mysteriously” the day after he spoke to investigators about Barnes’ murder.

More broadly, the Sun reported, they say the jury’s verdict after two days of deliberations went against the weight of the evidence.

“The only evidence presented constituted a collaborative guess by multiple witnesses that the defendant was involved in the murder of Phylicia Barnes,” the defense lawyers wrote in their motion for a new trial. “The only actual connection between the defendant and the killing itself was one witness whose credibility falls well below that of which any reasonable person could believe was telling the truth.”

The jury found Johnson guilty despite a lack of physical evidence. During the trial, Circuit Court Judge Alfred Nance expressed concern that the state’s case was based on circumstantial evidence but allowed it to continue.