Not proven is a verdict available to a court in Scotland.
View More on: http://en.wikipedia.org/wiki/Not_proven
Under Scots law, a criminal trial may end in one of three verdicts: one of conviction ("proven") and two of acquittal ("not proven" and "not guilty"). Historically, the two verdicts available to Scots juries were that the case had been "proven" or "not proven". However in a dramatic case in 1728 the jury asserted "its ancient right" to bring in a "not guilty" verdict even when the facts of the case were proven (see jury nullification). As the "not guilty" verdict gained wide acceptance amongst Scots juries, Scots began to use "not guilty" in cases where the jury felt the "not proven" verdict did not adequately express the innocence of the defendant. Shrewd defence then further encouraged this interpretation in order to persuade juries unwilling to bring in a "not guilty" verdict that the "not proven" could be brought in as a lesser or "third verdict".
The result is the modern perception that the "not proven" verdict is an acquittal used when the judge or jury does not have enough evidence to convict but is not sufficiently convinced of the defendant's innocence to bring in a "not guilty" verdict. Essentially, the judge or jury is unconvinced that the suspect is innocent, but has insufficient evidence to the contrary. However technically under Scots law (though not in the perception of the public) there is no difference between "not proven" and "not guilty" and both are equivalent to the "Not Guilty" verdict of English Law and of other jurisdictions.
Out of the country, the "not proven" verdict may be referred to as the Scottish Verdict or the Scotch Verdict, although in Scotland itself it may be referred to colloquially as the bastard verdict,[1] which was a term coined by Sir Walter Scott, who himself was sheriff in the court of Selkirk.