Under legal precedent, judges are supposed to decide the case in front of them similarly to the way similar past cases have been judged. The October American Journal of Political Science says students are biased to see cases with decisions they liked as more similar to any given new case.
We conducted two experiments: the first with undergraduates, the second with undergraduates and law students. Participants in each experiment read a mock newspaper article that described a "target case" involving unlawful discrimination. Embedded in the article was a description of a "source case" cited as legal precedent. Participants in both studies were more likely to find source cases with outcomes that supported their policy views in the target dispute as analogous to that litigation. … Legal training did not appear to attenuate motivated perceptions.
This suggests real judges similarly see cases as similar as needed to get the outcome they want.
Context independent similarity rarely exists, for good theoretical reasons found in choice theory.
Robin: Well, I could have told you that...
In all seriousness, I was struggling in the law library for several hours yesterday with just that issue. I had to stop and re-do sections because I would realize that a particular case didn't fit and whatever I was writing was just me wanting it to fit. This was slightly better than getting horribly confused because a judge had cited a case that said "In this situation, with facts X, law Y does not apply. But we agree with a sister circuit that law Y would apply with facts Z."
This judge citing the case had a case at bar that presented facts Z. So, one would think that law Y would apply, right? A case of first impression and he's citing a case that held "If presented with X, do not apply Y. If presented with Z, apply Y." No. This judge skipped the "If presented with Z, apply Y" bit and claimed that "We have facts Z, and a previous case held that law Y doesn't apply under facts X. I hold that law Y will not apply here."
Aside from that, it's very interesting, after reading large volumes of cases on a particular subject matter, to see how the judge's personal feelings towards a plaintiff or defendant, or the back stories of the plaintiffs and defendants creep into the opinions. I'll post the cites to the cases I referenced above if you're interested or lost in the tangles of a rather convoluted example.