Maintaining Fairness To Jurors

Dear fellow decentralized justice enthusiasts, the time has come to discuss an issue about maintaining fairness to jurors.

Currently, Kleros arbitrator lets evidence to be submitted until the dispute is resolved. Sometimes, this creates an unfair situation to jurors those who already voted if new piece of evidence gets submitted after they vote and this new piece of evidence changes the assessment of the dispute.

I would like to hear your opinions about how to improve the current system to avoid these unfair situations.

What should we do to fix this?

  1. Disable evidence submission after the evidence period.
  2. Add this phrase to court policy: “To ensure fairness to jurors who already voted, arbitration should disregard new evidence after evidence period. New discussions on old evidence are permitted.”
  3. Else?

Option 1 is more complied with our traditional rational and traditional legal understanding. But there should be more alert / notification to be implemented in order to help jurors not missing the critical period.

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I like the first choice. One potential problem would be one side trying to submit evidences near the deadline, so that the other party might not have sufficient time to reply. But I think it’s fine, that’s what appeals are for

How would number 2 be properly implemented? It’s in jurors’ best interest to consider subsequent appeals and choose the likely final winner :money_mouth_face:

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1 - It’s opens up evidence sniping, yeah. To prevent we can prolong evidence period after evidence submission if little time left. This opens up possibility to attack by submitting evidence forever to stall the dispute and to fight with this we can increase evidence submission fees monotonically, so after some time attacker can’t keep posting evidence.

2 - With this policy change, we align jurors vote in favor of disregarding new evidence after evidence period. But then it introduces this discussion: What is new evidence and what is new discussion on old evidence.

This seems like a really bad idea to me. Increasing the fees could enable an attacker to make submitting evidence really expensive which would silence their opponents/third parties. Submitting evidence should be as cheap as can be.

I don’t feel like we should restrict evidence submissions at all. It’s one of the most critical pieces of having a fair and just ruling

  1. I would propose, just like Ferit, a rule in general court, but slightly different. A rule that requires that all evidence should have been available (or reasonably easy to acquire) at the time of the submission. Rulings should also be based on the “state of the world” when the item was submitted.
  1. I would propose, just like Ferit, a rule in general court, but slightly different. A rule that requires that all evidence should have been available (or reasonably easy to acquire) at the time of the submission. Rulings should also be based on the “state of the world” when the item was submitted.

I generally agree with this, that we should have add a policy that is something like: “To ensure fairness to jurors who already voted, arbitration should disregard any evidence that was both submitted after the evidence period and could not reasonably be considered to have been readily, publicly available during the evidence period. New discussions on previously submitted evidence or evidence that was already publicly available during the evidence period are permitted.”

One of the common criticisms of Schelling point dispute resolution we hear is that well-informed jurors will have low expectations for the knowledge of other jurors and will vote in a way that they know is wrong but will expect other jurors to vote. This issue is largely resolved if a juror can make sure that whatever relevant, public information they have is available to the broader pool of jurors. (As a toy example, recall the cases we had about Venetian Doges during the Doges on Trial pilot: If we implement 1), that would not be possible. This is particularly relevant in cases like the exchange listing disputes where jurors are essentially being asked to decide based on information that is ultimately public, and exactly what any given juror looks at may vary.

On the other hand, with something like 3), we should already solve the most problematic aspects of evidence mutability - e.g. that someone creates a case against themselves where they intentionally hold back some “game changing” evidence that they reveal later in an attempt to win stake from crowdfunders, etc.


We are all talking about the time after the evidence period is over. I would like to point out that the same problem can be found when deciding what evidence is admissible during an appeal. There, again, we have the problem that the loosing party can introduce evidence that would change the outcome of the appeal that all jurors from the lower instance could not possibly have been aware of. This is even more problematic than when just looking at a single round since this allows a bad faith actor to trick the opposing party into spending unnecessary money on fees for the appeal. Some way has to be found to prevent this which means that there must be some requirements for evidence to be admissible.

Disabling evidence is an option that I would not recommend. First, it does not solve the problem for appeals and second it prevents discussions on issues of law. I consider the latter to be quite important since I believe that jurors should have some time to discuss issues of law once the evidence period is over and they know all the facts.

As a base rule therefore I recommend that evidence regarding matters of fact should be inadmissible after the evidence period in the first round of appeals ends.

Now let’s talk about the exceptions.

This point requires some discussion in my opinion. It states that a fair ruling requires that the court knows what happened. And I agree with that statement almost entirely. However, we must acknowledge that the parties naturally know most about the case and can therefore provide (or withhold) most of the relevant evidence and direct the attention of the court to certain aspects of the case. This power of the parties, in my opinion, needs to be sanctioned when they misuse it. With my general rule stated above I presume that the power is misused once the evidence period is over and a party still submits facts. The question is, when this presumption can be proven wrong.

I suggest that this presumption is wrong when the parties can show that it was impossible for them to submit the evidence before the end of the evidence period. Knowing the facts is a prerequisite for justice and giving them to the court in a timely manner is a duty of the parties.

Jurors who inform themselves from public sources should then decide whether they share their sources with the jurors - if they perform research on an aspect that was not yet thoroughly discussed - or if they consider that the research is such an obvious step in evaluating the facts that all other jurors will consult them as well. Jurors should not be incentivised to search for information that is not easily available if the parties do not point towards it since they cannot be sure that the other jurors will find them as well and because they know that the information will be deemed inadmissible if it is introduced by the parties later on.

By the way, jurors should, as marijn pointed out, rule on the state of the world at the time the evidence period ended. So changes that happended after that may not be considered.

My approach comes close to 3). Yet, I want to allow evidence that was not held back in bad faith. The difference between my concept and 3) eventually comes down to the question of who bears the risk of new evidence emerging. Is it a party who risks loosing a case it should have won just because a timer ran out? Or are it the jurors who already voted and who evaluated the evidence as good as they could and, without it being their fault, reached a wrong conclusion? 1) and 2) would shift the risk entirely to the parties. 3) and my proposal would shift it primarily to the jurors but seeks to strike a fair balance. I believe that my solution leaves a margin of appreciation towards the jurors when deciding what evidence they let in. Furthermore, that way the courts can develop some case law to cover all different scenarios.

This being said, I propose the following rule:

(1) Jurors shall disregard evidence on matters of fact that were submitted after the evidence period of the first round has ended.
(2) Submissions after that can be considered by the court if the submitting party can show that it was unable to submit the evidence in advance.

and - optionally

(3) Even when the conditions of paragraph 2 are met the court can reject an application if it would unfairly affect the outcome of the trial.

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I agree with the premise of this post.

Various strategic techniques if and when to submit the evidence.

I don’t like that in appeals, the voting starts immediately, without the time to prepare new evidence.

A lot of things, it would be a lengthy debate and I don’t have energy for that. I’m just saying - 100% valid point, I think it was discussed on Telegram already at some point.

I think the best option I heard so far is @William’s proposal.

Hi - as a matter of fairness and even-handedness to both the jurors and the disputants you need to set out at the outset a cut-off date for the submission of evidence.

A corollary of this is that disputants should be made aware from the outset that they need to line up their evidence within x days (a short period) from the submission of the dispute to Kleros. Apart from anything else this helps to prevent the ex post facto manufacturing of evidence.

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You should also consider making it a rule that disputants adopt a “cards on the table” approach to the submission of evidence. Evidence that is withheld / doctored gives the jurors a distorted picture of the dispute and prevents them from ruling in a manner that is just.

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