The elements of a crime are a series of components which must be present in order for it to be demonstrated that someone is guilty of a crime. The prosecution must provide supporting evidence to demonstrate that all of the elements of a crime are present in a given case and the defense can challenge the validity of a case on one or more elements.
Four key components must be present: intent, conduct, concurrence, and causation. Without one of these elements, a case can start to fall apart. This fact explains why sometimes the defense will freely admit to something which seems incriminating, only to still win the case; it accepts that one element was present, but denies other elements of a crime and uses these to deconstruct the prosecution's case.