Darn, it would!Would that work to defuse most general guilt-based panicking, do you think?
Still, it would depend on the company present. If it's a congregation of mobsters with a past.... who knows? But not very likely.
If the detective were to say such a thing, it will have an effect on the people gathered there. They'll start observe each other nervously... 'are you that child-murderer?' Not sure if this would help the detective, but perhaps you can use this to manipulate or insinuate others.
People will get nervous, suspicious, angry, affronted, drunk, thinking they can outclass or overrule that stupid little detective (1800's yes?). There will be emotions abound in a group of 50. A skillful person could play with that. But no guarantees, that I can see.