There's accusatory finger-pointing, constant courtroom interruptions by counsel and prosecutors objecting to/over each other, ultra-flamboyant characters, witnesses berating the judge (which normally renders you liable for contempt of court), and a near-impossible concoction of the adversarial legal system.
The protagonist's description as an 'ace' attorney is also... contentious.
Still, just to be sure, I checked Wikipedia.
Lo and behold, the courtroom differences between the game and the real-life Japanese legal system:
制作上の意図により、ゲーム中の裁判制度は2000年代現在の日本のものとは大きく異なる。例えば、本作特有の裁判のシステム序審法廷制度が最たるものだが、ほかにも異なる点がある。ゲーム中、裁判長の手にある木槌は実際の日本の法廷では使われておらず、「異議あり!」の発言も証人に向かって叫ぶのではなく、弁護士・検事が互いの質問・尋問に対して判事に申し立てるものである。しかし、本作のように弁護人や検事でない人物が法廷に立つことは、簡易/家庭/地方裁判所で「特別弁護人」として実際に認められている。
The court system featured in the game has diverged significantly from that of the present Japanese court system since the 2000s; for example, through the "Joshin System", which is the game's most characteristically distinguishing feature, and a host of other differing points: The wooden mallet in the hands of the judge, which is not used in real Japanese courtrooms, and the "Objection!" cries made towards witnesses, where in actuality, counsels and prosecutors mutually plead/forward questions and inquiries to the presiding judiciary. However, the part where a person himself stands trial in absence of counsel or prosecutor, that remains true for "special defense counsels", where quasi-/household/district courtrooms are concerned.
An additional note on the Joshin trial system:
『1』第2話から登場。逆転裁判の世界において、刑事事件の審理は、まず起訴された容疑者が有罪か無罪かのみを最長3日以内で審理する「序審」と、有罪が確定した後に被告の量刑などを審理する「本審」とに分れている。序審法廷制度はその制度の名称。増加する犯罪に対し、迅速に処理できるように制定された。ゲーム中で主人公が参加するのは全てこの序審法廷である。成歩堂は、この制度のことを「簡単にいうと最近、犯罪が多いから、ぱぱっと片付けちゃおうという制度」と説明しており、『4』で成歩堂はこの制度に対し疑問を投げかけている。
The Joshin system appears from the 2nd chapter of the 1st Gyakuten Saiban episode. In the world of Gyakuten Saiban, criminal trials come in two parts: first, "Joshin", where the accused is prosecuted and determined to be guilty or innocent within a time span of only three days, then "Honshin", where after guilt is ascertained, a separate trial takes place to determine sentencing. The "Joshin Trial System" is the general appellation for this, established as a speedy method of disposing cases in response to the increasing crimes. Within the game, all trials that the protagonist participates in come under this system. Naruhodo (the protagonist) himself explains, "To put it easily, because crime has been increasing as of late, it's a quickie system (for disposing cases)", though from the 4th episode he begins to cast doubt upon the system.