How do I go about setting up a trial/investigation mission?

Question

I have been running a freeform (no system, basic rules and sheets designed by yours truly), sandbox RPG with a friend of mine for about half a year now. It's my first GM experience and it's been running pretty good so far and I'm liking the one-on-one experience (it allows for permanent spotlight on the one player). All the experience I have is self-taught grit from this very 1on1 RPG.

Now, to add some variation to the missions and things my player can do, I'd like to set up a mission where you have to take a side in a court trial (either defense or prosecution) and investigate the crime scenes for evidence and clues. I'd like to try for the Phoenix Wright style of play, where there are moments you go out and investigate scenes and question people and other moments where you use your evidence and witnesses to prove the defendant guilty/not guilty.

What I'd like to ask now is:
How would I best go about making a trial combined with investigation and detective work? I'm specifically looking for a plan or template with which I can easily plan out a trial combined with evidence and witnesses.

• How do I set up a crime (and how do I make an innocent person end up as the defendant)? How do I best organise scenes, evidence and witnesses?
• How do I slip in lies and contradictions into witnesses' testimonies, like in the Phoenix Wright games (without tripping all the alarm bells of my player)?
• How do I best act out the opposing lawyer (and how do I manage the few pieces of evidence that the player may not have found)?

I have already figured out that some of the skills we have could be used for this, like Intrigue (figuring out conspiracies), Suspicion (seeing through lies) and Tracking (finding traces left by culprits or bystanders). I will likely use Suspicion and Intrigue to drop clues on my player if they succeed the test. Any suggestions on this bit are also welcome.

Finally, for your information, we are playing in a world with futuristic technology and magic. The trials will mostly take place in a region where magic is most prevalent but technophobia is also an issue sometimes (technology is still an option though).

Concerning my question, I've found two other questions which I did not find conclusive to my answer:

• Crime Investigation in a fantasy world

  This touches on some points in my question, but the issue is not the justice system, but rather how to plan it out.

• How to abstract a trial?

  This question gets really close and so do the answers. What it doesn't cover is how to plan out and organise the key witnesses and pieces of evidence in the trial. While I will allow leeway to have the player 'create' evidence and witnesses I didn't prepare, but I'd still like to have a roadmap to get the average story during the trial.

Answer 1

I'm not sure there is a single best answer for this situation but I'll try to give you some ideas.

• There is an RPG System called GUMSHOE that is entirely based around the idea of investigation.
• Don't let the PC choose their side. I can't really think of any real world context where someone could do this in an official capacity. They also have very different roles. It's the prosecutor's job to convict the guilty party, not prove someone guilty who they have found to be innocent. However a defender needs to find counters to the prosecutor's arguments and create doubt regardless of the client's innocence in the matter.
• If the PC is the prosecutor they should do all their investigation before the trial and you should give them a chance to encounter all the material the defense is going to present so that they can develop an answer for them. Then, as the prosecutor presents the evidence they can make rolls to convince the judge/jury, catch the witnesses in a lie, etc.
• As defender it would probably be more interesting to actually have the prosecution present each witness or piece of evidence and then do a flashback scene related to it. If they find what they're looking for then they can present it as a counterpoint, otherwise they have to use their social skills to try to convince the judge/jury that there's a reason the evidence/testimony should be overlooked. It need not be a one-for-one exchange either. A knife in evidence might be countered by a cigarette butt, an open 2nd-story window, and a witness who can confirm it wasn't there during the appropriate time frame.
• Functionally a trial is just a series of arguments and counterarguments. Overall, it being an RPG you can just make stuff up as it feels right but if you're having trouble you might try finding a mock trial kit (they typically rely on eye-witness and expert witness testimony and are generally annoyingly ambiguous) to adapt from. But don't be afraid to make stuff up to accommodate a really good roll.

That's all I have for now. I hope that helps.