Do Spirit boxes have any place in an investigation?
Apologies - I should have seen this earlier.
In a nutshell - No.
Whilst the device is worthy of research in itself, it should not be used in an investigation scenario upon which all output (from the device) is considered of paranormal origin.
My partner and I have undertaken many, many hours of research focused on the output from one of these devices.
Whilst some of the output has been very interesting, we cannot get away from the fact that the output is generated from radio stations *, so the argument that all responses, no matter how relevant and interesting, is simply random output from these broadcasts, is unavoidable.
* Yes - you could use a Faraday Cage BUT this has to be correctly constructed.