fishing expedition

fishing expedition   n.  An open-ended inquiry or investigation, often undertaken on the pretext of a minor or unrelated matter, whose real purpose is to uncover embarrassing or damaging information, as about a political opponent: "[enabled] prosecutors to expand what started out as an investigation of ... [a] land deal into a fishing expedition for intimate details of his daily—and nightly—life" (Margaret Carlson).

fishing expedition n. an exploratory search for facts. (This involves asking questions with no preconceived notion of what the answers might reveal.) : The lawyer was on a fishing expedition. There was no real wrong committed to justify a lawsuit.

Main Entry: fish·ing ex·pe·di·tion
Pronunciation: -"ek-sp&-'di-sh&n
Function: noun
1 : an inquiry (as by the use of discovery) that is unnecessarily extensive or unrelated to the lawsuit
2 : an investigation that does not stick to a stated objective but hopes to uncover incriminating or newsworthy evidence

fishing expedition

An attempt to find useful information by asking questions at random. For example, The sales force was told to go on a fishing expedition to find out what they could about the company's competitors. This expression was taken up by lawyers to describe interrogating an adversary in hopes of finding relevant evidence and is now used more broadly still. [c. 1930]