The rules here are really for Traveller/Cepheus/Andromeda/2D Systems but can be easily modified for use in anything else.

The Prosecution presents 3-6 Assertions.
Each Assertion must be answered by a Rebuttal. Rebuttals are not rolled for in court. They must be earned through investigation, contacts, expert testimony, legal research, cross-examination or flashback.
At the end of the trial, every unanswered Assertion counts against the defendant when the Verdict is determined.

A trial should not be reduced to a series of opposed Advocate rolls. The interesting part of a courtroom drama is rarely whether one lawyer is marginally more persuasive than another. It is the slow dismantling of a case: the witness who cannot possibly have seen what they claim, the forensic evidence which means something quite different once examined properly, the missing hour in the defendant’s movements, the inconvenient expert who explains why the prosecution’s apparently devastating evidence proves nothing of the sort. Courtroom adventures therefore treat the prosecution’s case as a collection of Assertions which the characters must investigate, challenge and ultimately rebut.

At the beginning of a trial, the Referee prepares 3–6 Prosecution Assertions. An Assertion is not simply a clue. It is a conclusion which the prosecution intends the court to accept, backed by one or more pieces of evidence. Spider-Man was present when Quentin Beck died is a fact; Spider-Man killed Quentin Beck is an Assertion. The prosecution might support it with webbing recovered from the body, an eyewitness who saw Spider-Man fleeing the scene, damage consistent with superhuman strength and evidence of a previous dispute between the two men. These things do not have to be false. Indeed, the best courtroom cases are built from evidence which is substantially true but which has been interpreted in the worst possible way.

The Referee presents the Assertions as the prosecution develops its case. They are not secret obstacles and the Referee should not treat the prosecutor as their own character in a contest against the players. The prosecution is the scenario. Its case has already been constructed. The characters’ job is to find weaknesses in it. Each Assertion may be defeated in one of three broad ways: Contradiction, showing that the evidence or claim is factually wrong; Discredit, demonstrating that the source cannot be trusted; or Recontextualisation, accepting the evidence but showing that it means something other than the prosecution claims. Recontextualisation is often the most satisfying. Spider-Man’s webbing really was found on the corpse, but because he fired a web-line in an unsuccessful attempt to prevent Beck falling to his death.

An Assertion cannot normally be removed simply by making an Advocate check and declaring it unconvincing. The characters need a Rebuttal, something concrete which can be put before the court. Rebuttals are obtained through play. Investigate might locate security footage which the police overlooked; Streetwise might find a witness who disappeared before giving a statement; Science might reveal that the prosecution’s forensic interpretation is impossible; Admin might uncover an improperly filed warrant; Persuade might convince a reluctant witness to testify; Advocate might discover that supposedly damning precedent was overturned thirty years ago. Contacts and Allies are particularly valuable during a trial, since knowing the right pathologist, journalist, police officer or retired judge can turn an impossible problem into a merely difficult one.

A typical attempt to obtain a Rebuttal is resolved as an ordinary 2D task check. Routine weaknesses may require 6+, substantial investigation 8+, difficult or well-concealed evidence 10+, and something deliberately buried or requiring an exceptional insight 12+. Use whichever characteristic and skill actually suit the method being attempted rather than insisting upon Advocate for everything. INT + Investigate may reconstruct a timeline, EDU + Science may challenge laboratory evidence, SOC + Advocate might persuade a judge to admit questionable testimony and even DEX + Electronics might be appropriate if somebody has to recover data from a damaged device. Good preparation, useful Contacts, appropriate equipment and information discovered elsewhere provide DMs as usual.

Effect matters. Effect 0 or greater normally produces the Rebuttal sought. Effect 2+ may reveal an additional useful fact, grant DM+1 when the Rebuttal is eventually presented, or expose a weakness in another Assertion. Effect 4+ can be devastating, perhaps completely destroying an important witness or unexpectedly supplying a second Rebuttal. Failure does not necessarily mean that nothing is found. A failed investigation may uncover the evidence but introduce a complication: the witness will only testify under protection, the document was obtained illegally, the expert has a damaging connection to the defendant, or presenting the evidence will open another line of attack for the prosecution.

Once discovered, a Rebuttal still has to be put before the court. If it is straightforward and admissible, this requires no roll; finding the answer was the challenge. If the prosecution can legitimately object, the witness must be broken under cross-examination, or the significance of technical evidence must be made clear to a hostile court, make an appropriate Advocate, Persuade or other social check. Success defeats the Assertion. Failure leaves it standing for now, although the characters may seek another Rebuttal or attempt a different approach. An especially strong Rebuttal may defeat more than one Assertion if the fiction supports it.

Courtroom scenes may also create new investigations. When a witness says something unexpected, a character can request a recess, send somebody to check the claim or trigger a Flashback. A Flashback is simply an investigative scene played out at the moment it becomes relevant: Earlier that morning, Foggy went to speak to the building superintendent… Resolve the scene normally and return to court with whatever was discovered. This keeps trials moving and avoids requiring players to anticipate every possible prosecution argument before proceedings begin.

At the end of the case, count the Unanswered Assertions. If none remain, the prosecution has failed to establish a meaningful case and an acquittal should normally follow without a roll. Otherwise make a final Verdict check, usually 2D + Advocate or Persuade + an appropriate characteristic, with a base difficulty of 8+. Apply DM-1 for each Unanswered Assertion. Particularly powerful Rebuttals, sympathetic judges or juries, favourable precedent and exceptionally effective closing arguments may grant positive DMs; prejudice, hostile publicity, prior convictions or judicial corruption may impose negative ones. The Verdict roll represents the uncertainty which remains after the facts have been fought over, not a substitute for fighting over them.

The Referee should remember that an acquittal is not the only possible victory. Charges might be reduced, some counts dismissed while others remain, damages drastically limited, a mistrial declared or the real culprit exposed in open court. Likewise, losing a trial need not end an adventure. An adverse verdict can create an appeal, a fugitive campaign, an investigation into corruption or the uncomfortable discovery that the court reached the legally correct decision for entirely the wrong reasons.

Most importantly, the Referee does not defend the Assertions. The Referee presents them honestly, plays the people involved and follows the consequences of the characters’ actions. The challenge comes from discovering how the evidence fits together, not from trying to out-argue a Referee who already knows every secret in the case. The prosecution brings the case. The characters take it apart.