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a case of mistaken identity

An instance in which one is thought or assumed to be someone else. Officer, this is a case of mistaken identity—I can assure you that I did not rob anyone!
See also: case, identity, mistaken, of

you (must) have mistaken me for someone who gives a shit

rude I don't care in the slightest about what you are saying. A: "Please don't discuss that topic on the air. You might offend some of our listeners." B: "Oh, I'm sorry, you must have mistaken me for someone who gives a shit." A: "I'm sorry, boss, but I don't know if I'll have the project done on time. I'm just dealing with a lot of personal issues." B: "You've clearly mistaken me for someone who gives a shit. Get it done by Friday, or you can look for a new job."
See also: for, give, have, mistaken, shit, someone, who
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

case of mistaken identity

the incorrect identification of someone. I am not the criminal you want to arrest. This is a case of mistaken identity.
See also: case, identity, mistaken, of
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

You must have mistaken me for someone who gives a shit

sent. & comp. abb. What makes you think I care about what you are saying? (Usually objectionable.) So you’re unhappy. Why tell me. You must have mistaken me for someone who gives a shit
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.
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References in periodicals archive ?
145-46 (discussing courts' disturbing tendency to treat mistaken contract interpretation as a mistake of law).
1981) ("A party is liable in trespass even though acting under a mistaken belief of law or fact, however reasonable").
DOBBS, THE LAW OF TORTS [section] 103 (2000) (writing that a person "who knows she does not know a fact is not mistaken about that fact at all").
34 (complaining that this "convoluted approach" of inferring mistake from sheer ignorance "bends of out shape" his carefully distilled definition of mistake discussed supra text accompanying notes 5-6); see also Sheehan, supra note 18, at 565 ("[Ignorance] cannot be transformed into a mistaken belief; there is no reason to take a lack of belief in X and make it a belief in not-X....").
The incomplete or incorrect diagnosis is a mistaken perception of the facts that exist at the time; the overly optimistic prognosis is a misprediction of the future consequences of the correctly diagnosed injury.
Despite Farnsworth's (flawed) perception that mistaken expressions are rare, see p.
538, 565 (2000) ("Opinions cannot be mistaken, as they relate to matters where there are no definite right and wrong answers.
Farnsworth declares the Marchese di Calatrava's killing to be accidental, rather than mistaken, because Don Alvaro intentionally threw down the pistol but neither intended nor foresaw the untoward consequence that the pistol would discharge, striking the Marchese.
21 n.15 ("In common parlance, the word accident is often used in a broader sense to include mishaps that result from mistakes, as where a collision resulting from a driver's having mistaken the significance of a traffic light is described as an 'accident.' "), but it undercuts Farnsworth's painstaking effort to define "mistake" and to distinguish mishaps caused by mistake from other mishaps, see pp.
(181) Mistakes are ubiquitous in law, as in life, and the excuses offered to relieve a mistaken party from civil or criminal liability are manifold.
Proving reliance on a mistaken transfer is generally easier than proving reliance on a contractual mistake because the former more typically involves the transferee acting in reliance, (179) while the latter more typically involves the promisee refraining from acting.
While "[c]laims to forgiveness are confined by considerations of relevance, risk, and fault," (177) a mistaken party's bid to reverse an alleviating mistake may fail because of some unmistaken party's interest.
The Restatement (Second) of Contracts advocates a no-fault approach to mistakes, except when the mistaken party already bore the risk of mistake or where his fault breaches his duty of good faith and fair dealing.
While both "commonsense justice" and efficiency-based jurisprudence argue that a party whose mistake is its own fault should not be afforded the same relief as an innocently mistaken party, Farnsworth finds little evidence that courts deny or restrict relief based on a mistaken party's fault (pp.
(167) An unabashed (pun intended) rule of risk assumption can be found in defamation law: one who utters a defamatory statement for the purpose of injuring another is tortiously liable even if the defamatory statement proves to be mistaken (p.