Dash camera,$40.
Get one that records front and rear,1080,and night vision.

Your passenger witness does not count
Biased/ conflict of interest etc

Thanks on the tip of not moving the car

And yes great idea on the dash cam

Sigh, same thing happened to me in the summer. I had my husband and daughter in the car, woman hits us on the side, and because I don't have a witness or there was no surveillance cameras, ICBC said it's 50-50 because the woman made up a lie. It was also my first accident after 18 years! So mad. Sorry you're going through it too.

If it's safe to, definitely take pictures. I was hit when at a stop sign (planning to take a right out of the parking lot). The other guy was turning into the parking lot and swung in unreasonably wide ( ironically also blasting Christian music from his car). He tried to claim 50-50.
I took photos from all angles . In that case a picture was worth 1000 words and dollars.

...if you ever see an accident happen, do the right thing and stop and offer your info to both parties as a witness. I did this earlier this year and the story of the faulty party (who fled the scene by the by) was wildly different to what actually happened. The cool part? Someone smoked my car while parking a couple of weeks back and thanks to a witness who left his info on my windshield the other party had no choice but to take responsibility. What goes around comes around.

until some idiot turns into you riding a motorcycle, puts you in the trauma ward for a week, comes to visit in the hospital insisting he was not in the wrong, and then draws out insurance for a year because he claims his wife got whiplash from the 5km/hour turn even though they find him in the wrong. Seriously, folks, icbc must help some of these peeps because they don't want to pay out.

ICBC is not your friend.
Once I was walking across the street and got hit by a car speeding through a red light. 100% his fault. Fortunately my injuries were minor, but when ICBC called me they asked if I missed any work, and I said no, and they said 'OK have a nice day' and that was it. Later I got a bill from the ambulance, and I also had to spend money on pain killers, bandages, polysporin, etc. I had to pay for all these things myself (and I was a starving student at the time). Meanwhile, the guy who hit me claimed $1000 in insurance because apparently he got a dent in the front of his beat-up 80s van where I had 'walked into it'.

Yeah, similar thing happened to my wife.

She was struck by a motorist while cycling and he lied to ICBC and the court.

Ones that are a mirror,and clip on over your rear view mirror and not so visible to invite theft.. $30 on ebay.