But MacLeod implies he asked a question during cross that they teach law students not to ask. Presumably because it's kind of a slam-dunk (and he got a slam-dunk response). But I'm curious as to why it's a bad idea to ask.
1. Lie
2. Rationalize (it wasn't perjury becuase x, y, z) (and which you are not prepared to counter-argue).
3. Take the fifth and refuse to answer.
Your better off getting there questioning various elements, and then presenting an argument that the signed document was invalid.
1. Did you witness the speeding?
2. Were you able to identify the driver of the car?
3. Please read this document (Plaintiff's exhibit A that states "I witnessed the speeding" and "I identified the driver of the car as x"
4. Is that your signature at the bottom of the document?
5. Are there any other signatures on this document?
Then you argue that since important elements in the document were in fact proven to be false, the document cannot be used as evidence that the defendant violated the law. Since there is no other evidence, the violation conviction must be vacated.
He can ask what evidence does the officer have to show that the author was in the car at that point of time when the photo was taken.
In order to get a 'yes', you need to convince the witness of your claim. And most cross-examinations either involve discrediting the witness, or leading them to provide evidence that helps the side they're not on. So they're rather biased.
If you ask it, and get a yes from the witness -- you almost certainly got enough from the witness for any judge/jury in the world to agree with you. So it doesn't really help.
When you don't get a yes, you're opening the door to the witness providing a different explanation for the things you've established. Which you don't want.
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In this case, Macleod had obtained everything he needed from the police officer to demonstrate that he had committed perjury. He could join the dots later, instead of asking the police officer to do so.
And although I'm not a lawyer, my understanding is that probable cause is a relatively low standard to meet, much lower than preponderance of the evidence and certainly much lower than beyond reasonable doubt.
Ask yourself this -- if a witness saw a car (and noted its license plate) parked in a house's driveway during the time when a burglary was likely to have taken place, and the car was unknown to those who lived at that address, would a judge sign a search warrant on that vehicle and the registrant's address based on probable cause?