I am an attorney and am pretty skilled at cross examining witnesses. At the negligence trial after a collision when the radar wasn't used the examination would go something like this:
"You had radar on your vessel didn't you?
And that radar was operating, correct?
And you know how to operate the radar?
And radar is caple of detecting other vessels in the vicinity of your own?
Your radar is capable of detecting a vessesl similar to the one you collided with?
Had you been monitoring your radar, you would have detected the other vessel before the collision, correct?
But you weren't monitoring your radar were you?
As a matter of fact, you didn't have your radar on did you?"
That is just off the top of my head, but get the picture?