This is a TV Trope, obvs, but it’s one that keeps cropping up.
On an episode of Vera, a British TV show that’s fairly formulaic but very well acted, the sergeant’s young daughter found a body on a train.
Early in the episode he apologised to Vera for not being able to be much help in the investigation, and I thought yay, that’s because his daughter found the body, so he has to be out of it, because otherwise he could feed his daughter information or the defence could claim he did. Then he’s back in the investigation again, and they take several days to even question the daughter. If I were on a jury I would not trust any evidence the daughter gave after that.
That wouldn’t come up in real life, would it? I could imagine that perhaps in a tiny rural area it might do due to resources, but this is a city.
Vera is not cheesy, and includes no comedy elements, FWIW.