Officer Frank White is accused of shooting Rachel Silva and her son in an Oceanside parking lot.
On Thursday, a war of words erupted in the courtroom as the prosecutor and a training officer engaged in testimony.
But the prosecutor said regardless of what happened, White broke protocol and failed to show his badge.
A lead detective also testified that Silva was hostile and profane when he tried to question her about the night of the shooting.
White said he was acting in self-defense. If convicted, he could face up to nine years in prison.