How to translate this 回避原则? context: 徐澄海一下跳了出来大声叫道：“ 这位警官，你和舒风是认识的！你们既然认识，就不能够插手干预这个案件。回避原则，难道你不懂吗？ ”
From context it looks like it's something like how in a court a friend or a relative isn't really a proper witness since they're presumably biased. Not sure what that's called though Actually an even better example would be Judges not judging cases involving their relatives and such where they'd have an obvious bias edit: seems like that's exactly it https://baike.baidu.com/item/回避法/15517896 though again I don't know what the English term for it is, if there is one The 回避 part seems to be called "Recuse" though. https://en.wikipedia.org/wiki/Judicial_disqualification
Principles of natural justice If an adjudicator breaches the rules of natural justice during the adjudication then the decision may be a nullity if the breach is serious. There are three well-known facets to the principle of natural justice: • no one should be a judge in their own cause • a party should be informed of the allegations against it and be given an opportunity to answer those allegations • a party is entitled to have its case heard by an unbiased and impartial tribunal
I concur with this. OP's excerpt is talking about recusing oneself to avoid a conflict of interest. So something like this: 回避原则，难道你不懂吗？ -- Don't you understand recusal?
I would prefer to rearrange and rephrase the whole line, but it's up to you. The previous answers are also great. "So you are indeed acquainted with Shufeng! Due to that fact, you cannot be considered an independent witness/party, and are thus unable to interfere with the case. Don't you even know that, dear Mr Policeman?"