Means, Philip Ainsworth, 1892-1944, American historian and archaeologist, b. Boston. An assistant on a Yale expedition to Peru (1914-15), he was later (1920-21) director of the National Museum of Archaeology at Lima, Peru. He traveled widely in Latin American countries, and between 1921 and 1932 he was several times an associate in anthropology at the Peabody Museum, Harvard. His works include History of the Spanish Conquest of Yucatan and of the Itzas (1917), Fall of the Inca Empire and the Spanish Rule in Peru, 1530-1780 (1932), The Spanish Main: Focus of Envy, 1492-1700 (1935).

In US Criminal law, means, motive, and opportunity is a popular cultural summation of the three aspects of a crime needed to convince a jury of guilt in a criminal proceeding. Respectively, they refer to: the ability of the defendant to commit the crime (means), the reason the defendant had to commit the crime (motive), and whether or not the defendant had the opportunity to commit the crime (opportunity). Ironically, 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.

Examples:

Say a man has stolen enough of my money to make me angry enough to want to kill him. If I am 10 miles away with a loaded gun when this event happens, I would have a motive (reason), means (the gun), but no opportunity (be physically close enough).

If I was standing next to that same man with nothing in my hands, and he is locked inside his car: I have no means because I cannot get to him inside the car, I have a motive because of what he has done, and I have the opportunity because he is close enough for me to kill him if I had say a gun (means).

If I was sitting inside the car with the man with a gun: I have means (the gun), I have motive (stealing my money), and I have the opportunity (sitting next to him in the car).