When the New York City police officer who tackled the former tennis star James Blake steps into a dim departmental trial room this week, Mr. Blake will have waited more than 700 days to see the officer answer for his actions since a civilian oversight board found that he used excessive force.

In the nearly two years that elapsed, Mr. Blake said he has canceled three plane tickets to New York because of trial delays and watched a plea deal he saw as soft fall apart for reasons that remain mysterious to many of the people involved. After the trial, Mr. Blake will wait again — likely for months — for the police commissioner to hand down a final ruling on the officer’s guilt and possible punishment. And in the end, details of the punishment could remain a secret.

The process, long and byzantine as it is, is the easiest path to holding an officer accountable for many victims of police misconduct. Overwhelmingly, they face bigger obstacles to pursuing a complaint than Mr. Blake, who was thrown to a Midtown sidewalk by Officer James Frascatore two years ago after he was misidentified as a suspect in a credit card fraud ring.

But new data obtained by The New York Times shows just how long it takes for the Police Department to decide on an allegation that the Civilian Complaint Review Board has substantiated. Among the 43 trial cases that concluded this year, complainants waited an average of 454 days, or roughly 15 months, for prosecutors and defense lawyers to rest their cases at trial. And after that, they waited another 201 days, or roughly seven months, for a departmental judge to get comments and issue a ruling, and for the police commissioner to decide whether to uphold the verdict.