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[1940] 1 KB 4. At common law, a defendant in a criminal trial could only have his bad character exposed by prosecution witnesses if the defendant put his own character in issue (see putting character in issue). In this case it was held that casting imputations on prosecution witnesses did not amount to putting the defendant's character in issue; consequently, provided the defendant does not testify (which would bring the provisions of the criminal evidence act (1898) into play), the defendant can malign any witness he likes in any way, and not have his own bad character exposed.

The Butterwasser ruling will be reversed when the Criminal Justice Act (2003) comes fully into force -- under s.101(1) a defendant becomes subject to evidence of his bad character being adduced whenever he 'makes an attack on the character of another person'.