According to the ESRB, this game contains: Blood, Language, Suggestive Themes, Violence
Parents should be aware that Phoenix Wright: Ace Attorney is definitely geared towards the older gamer. It can be difficult and frustrating, requiring a high level of reading, logic and comprehension skill to be successful. As far as language goes, I don't think the level of profanity ever got more explicit than "damn", although there are a few double entendres and a lot of sarcastic and irreverent comments. From this aspect, I would say that this game is completely harmless. As far as the violence goes, there are a few scenes involving blood or dead bodies, once scene showing a stabbing, and one of a gunshot, if memory serves. None of it is very graphic, but it might not be entirely suitable for younger gamers. However, I will say that if your children are smart enough to play this game in the first place, they are probably old enough to handle the very mild content.
Players looking for something different will absolutely want to check out this game. Well-done graphic adventures are scarcer then hen's teeth, and the premise of being an attorney, as far as I know, is absolutely unique in the realm of videogames. The characters are excellent, the crimes are intriguing, and the challenge of proving your case in court is something that admirers of the odd are sure to dig.
Deaf and Hard of Hearing gamers will have no problems. The game is presented fully in text, with just a few voice samples scattered here and there when raising an objection, and so forth. Nothing is lost by playing with the sound completely off, and the entire experience is fully accessible from a silent standpoint. No barriers here.