People scream for lots of reasons. I could argue that being murdered is the least likely reason for someone to be screaming. Some legal systems err or the side

People scream for lots of reasons. I could argue that being murdered is the least likely reason for someone to be screaming. Some legal systems err or the side of "innocent until proven guilty" but you're leaving the last part off, "beyond a reasonable doubt". There's no need to establish a motive for a crime. I believe it may strengthen the case against you but it's not like you can get off for committing a crime just because they couldn't establish a good reason for you to have done it. "So, Mr. Chayote, why did drop that anvil on my client's head, Mr. Roadrunner?", "No reason, that's just what I do", "Case dismissed due to lack of motive!"