"I’m very sorry that my statement is wrong, my Lord, I was just basing it on memory and guesswork, and Hartley did say it would be alright..."
You're ignoring the statement. If a police officer isn't sure, he says so, using commonly-recognised language that implies as much, or he doesn't give a statement at all. If you say, or imply, that you are sure about something when you aren't, that's called lying.
I appreciate that witnesses will sometimes affect to be sure of things when in fact they're relying on memory, and that in itself is not necessarily lying, but this is a bureaucratic matter for which the police have records and pocketbooks. Whether it's 10 records or 600 is neither nor there.
As usual, you're missing the point.