There are a plethora of judicial attempts to define an abuse of discretion. For the most part, the phrase is a term of art in American law; a threshold at which a tribunal's decision is exposed to mandamus, certiorari or such other review by an appellate or superior-level court.
In US v One Star, Justice Selya used these words:
"An abuse of discretion occurs when a material factor deserving significant weight is ignored, when an improper factor is relied upon, or when all proper and no improper factors are assessed, but the court makes a serious mistake in weighing them....
"[A]n error of law is always tantamount to an abuse of discretion."
In Sharpe, Justice King's attempt at definition-making:
"An abuse of discretion can flow from a failure or refusal, either express or implicit, actually to exercise discretion, deciding instead as if by general rule, or even arbitrarily, as if neither by rule nor discretion."
This, from Justice Forrester of the United States Court of Appeals in 2007 (US v Merrill):
"An abuse of discretion arises when the district court's decision rests upon a clearly erroneous finding of fact, an errant conclusion of law, or an improper application of law to fact."
In Re Brewer Leasing, Justice Alcala upped the ante by requiring a clear abuse of discretion:
"Mandamus relief is available only to correct a clear abuse of discretion when there is no adequate remedy by appeal.
"Clear abuse of discretion occurs when a trial court reaches a decision so arbitrary and unreasonable as to amount to a clear and prejudicial error of law."
In Khan, Justice Pooler of the United States Court of Appeals had before him an application to reconsider the decision of an immigration tribunal. On the issue of an abuse of discretion, he wrote:
"An abuse of discretion may be found in those circumstances where the Board's decision provides no rational explanation, inexplicably departs from established policies, is devoid of any reasoning, or contains only summary or conclusory statements; that is to say, where the Board has acted in an arbitrary or capricious manner."
In Marshall, Justice Kirby of the Court of Appeals of Tennessee preferred these words:
"An abuse of discretion occurs when the decision of the lower court has no basis in law or fact and is therefore arbitrary, illogical, or unconscionable."
- In re Brewer Leasing, Inc., 255 SW 3d 708 (Court of Appeals of Texas, 2008)
- Khan v. Gonzales, 495 F. 3d 31 (United States Court of Appeals, 2007)
- Marshall v. Cintas Corp., (2007), 255 SW 3d 60 (
- Sharpe v. Director, OWCP, 495 F. 3d 125 (United States Court of Appeals, 2007)
- US v. Merrill, 513 F. 3d 1293 (United States Court of Appeals, 2008)
- US v. One Star Star Class Sloop Sailboat, 546 F. 3d 26 (United States Court of Appeals, 2008)