R v Lifchus, [1997] 3 SCR 320 is a leading Supreme Court of Canada decision on the legal basis of the "beyond a reasonable doubt" standard for criminal law.

William Lifchus was a stockbroker who misrepresented the value of a bond in his personal margin account to his employer, defrauding it of a substantial amount of money.

There were four issues before the Court: 1) Must a trial judge provide the jury with an explanation of the expression "reasonable doubt"?

4) If the charge in this case was insufficient, ought this Court give effect to the curative proviso set out at section 686(1)(b)(iii) of the Criminal Code?

Cory provides a series of principles upon which a trial judge must formulate their definition of "reasonable doubt" to a jury.