The information, sent to Baltimore prosecutors on the day after Michael Maurice Johnson was found guilty of killing the visiting North Carolina teen, contains statements that the defense says shows McCray — whom they described at trial as a "jailhouse snitch" — is not reliable. They say the new details add weight to Johnson's request for a new trial.
Johnson was convicted of asphyxiating Barnes, 16, shortly after Christmas 2010 and dumping her body in the Susquehanna River.
The information from Montgomery County also sheds more light on McCray's broad history of collaborations with law enforcement, often based on information he had picked up while in prison.
At trial, prosecutors were open about McCray's previous involvement in criminal trials, and argued that convictions in other cases showed he could be relied upon. He testified that he had helped out in a Montgomery County rape case and an Alexandria, Va., murder case.
But notes from a Montgomery County detective suggest McCray's career of cooperation was more extensive and not always as successful. In a recent court filing, Johnson's attorney's wrote that the new details show that other police had judged him not to be credible.
Baltimore prosecutors said in a response that the detective's notes on McCray were marred by inaccuracies. "The information provided in the recent disclosure from Montgomery County is hardly impeachment and is immaterial and irrelevant to the instant case," assistant's states attorney's Lisa Goldberg and Tonya LaPolla wrote.
The lawyers in the case remain under a gag order and declined to comment.
Prosecutors first learned of the new claims about McCray when Montgomery County Deputy State's Attorney John M. Maloney wrote on Feb. 7 that he might have been a witness in case handled by Maloney's office.
Maloney was referring to a murder case, according to the letter from Goldberg to Johnson's defense team.
The letter from Montgomery prosecutors makes no judgment as to McCray's credibility but does note that the state "ended up not calling the witness."
In notes provided with the letter, Montgomery County detective Dimitry Ruvin said he had looked into two other murder cases in which McCray said he had information. But in both cases, law enforcement officials told Ruvin that McCray's stories contained inconsistencies.
Ruvin added that detective Rosa Ortiz from Arlington, Va., told him that McCray had also been a witness for Metropolitan Police in D.C. in "several cases however he was found not to be credible."
Ruvin, Ortiz and Maloney could be reached for comment.
In a letter to Johnson's lawyers, Goldberg wrote that the Baltimore state's attorney's office investigated the claims and came to the conclusion that "nearly all the information contained in Detective Ruvin's memo is incorrect."
McCray was not called in the Montgomery County case, she wrote, because he could not be located, not because of questions about his credibility.
Ortiz also told the Baltimore prosecutors that she had been told by a Washington, D.C., detective that McCray had provided credible evidence in the past, Goldberg wrote.
McCray is currently in prison on a Charles County theft conviction.
He testified at the Barnes trial that he knew Johnson through an underground business he ran. Johnson called him to his apartment, McCray said, and he saw Barnes' dead body there and gave Johnson tips on disposing of it and evading police.
He testified at trial that he decided to come forward to tell what he knew about Johnson when struck by pangs of guilt while reading the Bible.