From Wikipedia –
“In US Criminal law, means, motive, and opportunity is a popular cultural summation of the three aspects of a crime that must be established before guilt can be determined in a criminal proceeding. Respectively, they refer to: the ability of the defendant to commit the crime (means), the reason the defendant felt the need to commit the crime (motive), and whether or not the defendant had the chance to commit the crime (opportunity). Opportunity is most often disproved by use of an alibi, which can prove the accused was not able to commit the crime as he or she did not have the correct set of circumstances to commit the crime as it occurred. Motive is not an element of many crimes, but proving motive can often make it easier to convince a jury of the elements that must be proved for a conviction.
Establishing the presence of these three elements is not, in and of itself, sufficient to convict beyond a reasonable doubt; the evidence must prove that an opportunity presented was indeed taken by the accused and for the crime with which he or she is charged. For an example, consider this ruling in the case of a suspect accused of robbery and assault:
… evidence of motive, means, opportunity, and consciousness of guilt are not enough to establish guilt. Compare Commonwealth v. Mandile) (evidence of motive, means, unexplained possession of property, and consciousness of guilt not enough to establish robbery). Nothing in the record sufficiently links the defendant to the crime to permit the conclusion beyond a reasonable doubt that he was the perpetrator.
Contrary to popular depictions in the fictional media, the court cannot convict merely on these three famous elements, but must provide convincing evidence, and opportunity actually acted upon by the defendant charged.”
From ShiningInLuz –
I prefer to take the proposal of an abduction in the order Motivation, Means, Opportunity. AFAIK in a crime, you tend to have someone in the frame, then work out why it was important to them. And then, assuming you can, you nail motivation. I am forced to do it the wrong way round, to start at the wrong end.
Of all of the interrogatives (question words – who, where, when, what, how, why) motive simply looks at why.
Why would someone enter apartment 5A and kidnap Madeleine McCann? This will be the point, as Wikipedia shows, that is as wobbly as trying to nail jelly to a board.
Without a concrete suspect, trying to establish a said suspect’s motivation is pure speculation.
Nonetheless, I want to have a crack at motivation, simply to show that motivation on its own brings up numerous problems and numerous questions.