Summary

• I describe how the trial process plays out in a courtroom. This post is part of a series on my experience serving as the foreperson for a jury trial. See also "Part 1: Jury Selection" and "Part 3: The Verdict".
• Consistency as a meta-goal of rule of law explains much of the processes we see in our legal system. The goal is to minimize arbitrariness and personal bias.
• We should consider the base rates of wrongful convictions and active deception when weighing how much to trust witness testimony.
• Judges are the interpretation layer of the law, and rule on the specific legal/procedural questions that come up during a trial, like whether a specific piece of evidence is admissible.

Opening Statements

We now enter the trial process! Depending on how late jury selection ran into the day, the trial may begin immediately after a short break or the next morning.

The counsel again stand until all members of the jury are present. Then everyone may sit for a moment to rest their legs.

Then the court clerk calls the courtroom to order, and the judge enters, for which everyone again stands. The ceremony is part of the point. The judge is the law personified in the courtroom, and everyone is standing to respect the rule of law.

Legal counsel for the plaintiffs/prosecution, who initiated the case, will give their opening statement. The respondents/defendants' legal counsel will give their own opening statement afterwards. Depending on what the judge decides, the attorneys may or may not be allowed to use a slide-deck.

The opening statements themselves are meant to be an overall framing of the argument that each side plans to put forward. The judge will remind the jury that the opening statements are not themselves evidence, but instead an interpretation of the evidence to be presented. The jury's job is to keep an open, skeptical mind throughout the trial.

Evidence: Testimony and Exhibits

The legal drama continues as the plaintiffs/prosecution call Witnesses to the stand or present artifacts. These artifacts are called Exhibits and numbered for later reference. Both are referred to as Evidence.

Witnesses are sworn in under penalty of perjury, i.e., being caught lying will carry severe penalties. To my surprise, even the least-credible witness in my trial never tried to lie directly. They instead dissembled with "I don't recall", "I'm not sure", and so on. Oaths and cross-examination (when counsel for the other side questions a witness) are powerful!

And yes, this is where the attorneys will object, often on the grounds that testimony or exhibits are irrelevant to the case. The judge will rule on the admissibility of evidence based on pre-set rules, and may instruct the jury to ignore what was said/seen. Objections may also be to the behavior of the other attorneys or witnesses, which can be very entertaining to watch.

This is why having an excellent judge is so key: they are the interpretation layer of the law, and their rulings are what determine what is allowed or not within the courtroom.

There are a few other players present throughout the trial:

• A court reporter is using a stenograph to transcribe what everyone says during the trial. When people say, "For the record", this is what they mean.
• A bailiff may be present to maintain order in the courtroom, especially for criminal cases.
• An audience may be present, but must be silent throughout.

In addition, depending on the judge, the jury may have an opportunity to submit questions after both sides finish their questioning, cross-examination, and recross. The judge and attorneys will review these questions before the judge asks them on behalf of the jury, which is otherwise silent throughout the trial.

Lastly, if you have a really exceptional case, the judge may arrange for everyone to go visit the scene of the incident together.

Aside: Witness Testimony is Evidence

I want to pause for a moment to discuss something that surprised me during deliberations later on, which was how skeptical some of my fellow jurors were of witness testimony.

Jury instructions (federal example, state example) are clear here: witness testimony is evidence to the degree you find it credible. But the lawyers in the group had to remind a couple folks of this, who seemed to discount testimony altogether.

My instinctive reaction was the tautology of survival in evolution: X can't be grossly off, or else we wouldn't be here [selection-bias]. If most people actually lied to each other in such formal, high-stakes settings all the time, we wouldn’t make it this far as a species. Even the least-reliable witness on the stand during this trial had to fall back to evasive non-answers under cross-examination rather than outright lies.

What about all the ways witness testimony can be unreliable? There's been plenty of grueling, amazing work to successfully exonerate the innocent. It turns out that people sometimes confess to crimes they did not commit, it's easy to inadvertently distort the process of picking someone out of a line-up, and so on. All of that is before you even account for racism or any other discrimination.

Still, here's why I think the default discount rate for witness testimony should be something like 30% and not 90%:

(1) Selection bias for miscarriages of justice will distort their perceived prevalence. Most people don’t get books and podcasts written about them. The Innocence Project points to research showing a false conviction rate of 4-6% for capital crimes (original sources one + two). Whether you think that's too high (my position), too low, or just right points to the inherent trade-off between letting the guilty walk free and convicting the innocent [failures-tradeoffs].

(2) Witness testimony can be reliable on general patterns and ongoing interactions. “He’s always been on-time” should carry more weight than “I saw this person wearing these clothes in the dark” or “The number was $123 from this invoice I last saw 5 years ago”. (To be clear: these are all made-up examples and not from the case I participated in) If someone has many observation opportunities, then any initial noise will average away over time. You will still have to watch for systemic biases and ulterior motives.

(3) Deception is the dark matter of truth. Even if someone is actively seeking to deceive, that is a useful signal. As a juror, this can be more than just a reason to weigh their testimony less overall. It can actually be a vector towards the truth.

Let me give a crude but hopefully memorable example for this last point.

Lying Towards the Truth

Let’s jump back to 14th century Europe. Primogeniture, the feudal system, and absolute monarchies reign supreme. Our modern conceptions of who counts as a person and their fundamental rights are centuries away. Amidst this backdrop, King John XIII sets out on a massive pubic relations campaign. He erects massive phallic statues in his honor. He has the royal physician issue a proclamation of his virility and stamina. He commissions a massive, "to-scale", anatomically accurate oil painting of his member by the royal artist. Anyone who speaks or writes to the contrary in a public setting is beheaded.

Meanwhile, private letters between his mistresses and their other lovers giggle at John. And public bathhouse graffiti abounds, making fun of how he can’t get it up, can’t last, and has terrible technique. What do you think is the truth of the matter here?

I’ve given a flippant historical hypothetical, but this applies on a contemporary basis to e.g., (counter)intelligence operations that have to assess whether their sources are feeding them false intel. The point is that lies implicitly gesture towards what's being hidden or changed. The meta-point is that humans have had to deal with deception for time immemorial and we’re not helpless in the face of it.

I'll close this aside with another meta-point: don’t collapse dimensional properties (trustworthiness of testimony) into binary buckets (100%; 0%). This is mental shortcutting and a good way to lead yourself astray. Ultimately, you weigh all the evidence, and it would be foolish to always apply a total discount rate to witness testimony.

Closing Statements

Back to the trial.

You've heard the evidence! Now hear from the attorneys for the final time, as they argue why you should find in their favor.

Our trial saw one side do an elegant full-circle, pointing out how their presented evidence matched what they promised in the opening statement. The other side confidently rebutted, pointing out gaps in the evidence and the other side's case, and argued for a different interpretation of what the law required instead.

Again, the closing statements are not evidence, just interpretations of it and the law.

By now it's clear why the attorneys have been standing respectfully every time the jury returned from a break or for a new day. You are the deciders of the case, and it is in their best interest to win you over.

Next up: reaching a verdict.

Read the rest of the series: "Part 1: Jury Selection", "Part 2: The Trial" , "Part 3: The Verdict".

Footnotes

[selection-bias]: I still haven't figured out the right catchphrase for this idea, which is a combination of survivorship bias (itself a subset of selection bias), the anthropic principle, and the Lindy effect.

[failures-tradeoffs]: This is somewhat tangential, but one of my favorite reads is by psychiatrist Scott Siskind on the "Ontology of Psychiatric Conditions", which gives a set of mental models on how to think about psychiatric disorders. In particular, one of the articles discusses "trade-offs vs. failures" for why evolution has not eliminated them, and uses a justice system metaphor to explain trade-offs. That metaphor is a very simplified example of the ethical considerations that apply to setting up a justice system.