However, two prosecution experts later repudiated some of their testimony and said that based on new scientific views, the evidence didn't clearly rule out an accident.
Yesterday, a state judge set aside Johnson's conviction.
"I'm hoping for a positive future — for my life to begin," Johnson said in a statement released by his lawyers after that ruling.
Johnson will remain free while prosecutors decide whether to seek a new trial.
His is among a nationwide series of recent legal challenges to what used to be accepted evidence of "shaken baby syndrome".
At least 14 people nationwide had already been exonerated since 2011 in shaken baby cases, lawyers said, citing the National Registry of Exonerations. Northwestern University's Medill Justice Project said in 2015 that there were more than 3000 shaken baby syndrome cases in the US, though lawyers said it's not clear how many might have resulted in wrongful convictions.
"Research and scientific studies conducted after the date of Zavion Johnson's trial have altered the opinions of the prosecution experts," Sacramento County Chief Deputy District Attorney Steve Grippi said. "A prosecutor's duty is not simply to win cases but to ensure that each defendant is accorded procedural justice and guilt is decided upon the basis of sufficient evidence."
Johnson's lawyers have already filed a motion seeking to have any new charges dismissed at his next hearing on January 20, based on a lack of evidence beyond the experts' medical testimony.
-AP