Gyakuten Saiban: Sono "Shinjitsu", Igi Ari! Season 2

Synopsis

Phoenix suffers a blow to the head from behind and loses his memory right before a trial, in which he is defending police officer Maggey Byrde for the murder of her boyfriend and fellow officer Dustin Prince. Despite his amnesia, Phoenix finds several contradictions in the evidence presented that implicate the key witness, Richard Wellington, as the true murderer. When Wellington's motive is brought into question, Maya arrives with evidence that Wellington is part of a con artist group, killing Prince out of fear that he would find the group's contacts on his missing phone, which Maggey found on a date with the in-uniform Prince. As Wellington states he has already recovered his phone, having attacked Phoenix in order to do so, Phoenix regains his memories and reveals that the phone Wellington took is actually his own, leaving Phoenix with Wellington's phone and proving Maggey's innocence.

(Source: Wikipedia)