Even for crime scenes not a single soul had witnessed, "things" would undoubtedly remain. Manalee would use her powers to converse with those objects, and there was thus no mystery she could not solve. The rusted lamp, or the broken crate, even the moldy floor she found would provide her with the answers she sought. Culprits could only hope that particular detective was not to follow, for if she did, there could be no escape.
See Great Sleuth Manalee.
Manalee is probably a feminine name of Hebrew origin, a variant of Hebrew name Mana "God is with us" with the suffix lee. Or it could be a variant on Hindi feminine name Manali, which translates from Sanskrit as "bird".