District Attorney Larry Krasner made the announcement on Wednesday.
The conviction stems from a traffic stop in Northwest Philadelphia in April 2021.
Former Officer Daniel Levitt said he saw a gun sticking out of a bag and a passenger was charged for not having a license to carry.
But Krasner says evidence shows the gun was not in view.
"Why does it matter? It matters because the case goes away if you tell the truth. Why does it go away? Because it is a violation of individual rights to search that bag without legal authority," Krasner said.
Sentencing for the former officer is expected in August.