the meaning of "on a technicality"

[kjc0123]

What is the meaning of "on a technicality" in the sentence "Scopes was convicted but released on a technicality"?

[Quizmonster]

There are many technicalities involved in the administration of the law. For example, information about a crime might have been gained by using some illegal method such as telephone-tapping. Once a magistrate or judge is satisfied that this is what happened, the case against the accused will be thrown out. He may well be guilty, but he must be released 'on a technicality'.

[New Forester]

This is one reason why charges often include complex phrases like "on or about" a date, "known as" a name, or "alone or together with person or persons unknown". Every eventuality has to be covered. You'd not want to find yourself with a culprit, solid evidence that it was him and others, and you've gone and charged him with having done it on his own. There was a famous murder case in the 19th century, against I think a member of the House of Lords. If I remember right he was charged under a slightly wrong name, and was therefore let off on that technicality despite there being ample evidence to convict.