What impact does having marijuana in your system when you are injured and it results in a personal injury claim?

Your legal thinking is correct. If it is not a factor, it should not be an issue. But nobody will be able to promise you what a judge will decide re admissability.

You should, I feel, expect that the attys on the other side to be told. So it will not be a secret.

Even if not a factor in causing the accident, there may be legit arguments that it effects the other half of the equation -- the what you lost part.

Your atty should be able to help you with some more detailed guesses when you talk.

What you need to know about mj is that even if you haven't ingested any lately, metabolite from mj is stored in your body for a long period of time (for heavy users). You thus need to be careful about driving and doing other things where someone might claim your ability is impaired. The metabolite is not active and you are not stoned but it is there and measurable. I have had several "rolling stoned" dui cases where the driver hadn't smoked in weeks. Watch out.