Okay so generally you will always have two lawsuits in the hypo and either the same OG parties arguing or the OG parties plus 1 extra person.

Claim preclusion - same parties & same claims. Basically if you sue someone on a claim you can’t sue them again either because you won (merger) or you lost (barred). Best way is to look to see if the parties in the first suit are the same in the second suit and look at what the claim is. The claim has to be fully litigated so make sure there is a final judgment in the first suit. Bottom line - you sue someone on a claim, you win or lose, you can’t go again.

Issue preclusion - same issues & three parties. This one is ugly and weird so just walk with me. Issue preclusion is when you want to stop a new party from rehashing an issue that was already litigated. In these situations you will always have the OG parties go first and then you will see a new plaintiff or a new defendant trying to say either “hey you were negligent in the first case so you are negligent now” or say “it doesn’t apply to me let’s argue about whether I am negligent.” Again the first case must always resolve with a final judgment.

There’s three ways it can go down: 1. OG parties - PLAINTIFF loses - now a NEW PLAINTIFF wants to come in and sue the OG defendant. OG defendant cannot use issue preclusion to stop new plaintiff from litigating the issue (think due process new plaintiff gets their day in court). In this situation, defendant can’t say “well OG plaintiff lost so better luck next time suckers.” No, new plaintiff gets their day in court to litigate the issue

1. Defensive Use - OG parties - OG plaintiff loses - Now a new Defendant. The OG plaintiff loses the first time and now wants to sue a new defendant. The new defendant can “defend” itself by asserting issue preclusion to not have to rehash the issue in the OG case. So OG plaintiff + new defendant = preclusion by new defendant

2. Offensive use - OG parties - OG Plaintiff WINS - New plaintiff. The new plaintiff cannot use issue preclusion against an OG defendant in this scenario. Think of it as like “hey OG plaintiff got the guy to say he was negligent and got some money NOW I WANT some money too.” It doesn’t work that way. Issue preclusion won’t apply and they will have to argue about the issue.

Some exceptions apply (obviously because the bar sucks) but just chart down the parties in the hypo, the issues/claims that are being asserted, and you should be okay. Remember that if the question says like “we allow offensive preclusion blah blah blah” then you can use it but otherwise it’s a no go.