Multiple demerit “nominations”

Hi all, I’ve had a failed attempt at nominating demerit points to someone who was driving my vehicle at the time and using a phone. I received a letter after this failed stating that further nominations will be monitored.

My partner was recently driving my car and got done doing a u turn. I only received the failed nomination letter AFTER they did this but now I’m scared to nominate him. How do they further monitor this? We were all in the car at the same time but he was definitely in the driver seat. Can I get in trouble given that the last person basically lied and now I’m nominating another person for the next offence???