33-year-old Ryan Gilroy, of Colchester, was due to stand trial in October at Chelmsford Crown Court.
Essex Police, who suspended him pending the outcome of the trial, have now confirmed the case against him has been discontinued.
The force said the charge was dropped because of “evidential reasons relating to an administrative error”.
Gilroy had denied the charge.
He remains suspended, and Essex Police misconduct proceedings are ongoing.
