A partner or assistant is a character who accompanies the player character in investigation phases of the Ace Attorney games. Originally an unofficial and colloquial concept used to refer to a character who accompanied Phoenix Wright, Mia Fey, Apollo Justice, or Athena Cykes in their investigations and trials, the release of Ace Attorney Investigations: Miles Edgeworth explicitly refers to "partners".
Role[]
In the main series, the player can usually talk to the partner directly at the Wright Anything Agency / Wright & Co. Law Offices. Generally, the topics of conversation in these situations are "What to do" and "Any ideas"; that is, the player can ask the partner for hints on how to start the investigation. The partner also usually travels alongside the player character rather than only being interacted with at any one accessible location, and can engage in the player character's conversations with other people or talk about an object being examined. In The Great Ace Attorney Chronicles, they give comments in the Move screen.
Generally the partner will also be the protagonist's co-counsel during trials, but sometimes this is not the case. The reverse is also true, as some characters may aid the protagonist in trial, but not during an investigation, although this is generally reserved for trial-only cases. They talk to the player during the trial, participate in trial conversation, and give the player hints during a cross-examination after going through each statement. Incidentally, "co-counsel" is purely a real-word term applied to people who share in the duties of defense counsel with the main defense attorney, and the term is not actually used in the series.
In Ace Attorney Investigations: Miles Edgeworth and Gyakuten Kenji 2, the partner is clearly identified. The partner's sprite follows Miles Edgeworth's or Gregory Edgeworth's sprite as the player moves them around. The player can press "Y" or the "partner" button on the touchscreen to converse with the partner. During both The Imprisoned Turnabout and The Grand Turnabout, Little Thief occupies the "partner" button, and it is used to switch between two different re-creations of the same crime scene. Other objects also have taken up the partner button, such as Dick Gumshoe's metal detector and Ema Skye's bottle of luminol. However, these are only used to go over explanations of the item in question with their owner. A few partners do not follow the Edgeworths around, however, but still function identically to them (i.e. the "what to do" and "any ideas" conversations and traveling with them to a different area).
In Professor Layton vs. Phoenix Wright: Ace Attorney, the investigations are based on the Professor Layton series, so there is no distinctive "player character" (and thus no distinctive "partners"). In the lower screen, all the mini-sprites of the party characters are displayed, and the character on the far left can be considered the leader of the party.