Ask the Attorney: Crash liability

Atty Haymond,
I was involved in a terrible crash when someone ran a red light and hit me almost head on.
I've been incapacitated for over 3 weeks from the collision and I just found out they are claiming
it was me who ran the light!
Would you please give me some guidance on what I should do,
I'm not sure if there were even any witnesses?

Courtney C