It is suggested, in connection with this murder investigation, that luminol evidence is not useful, that it shouldn't be trusted, that it means nothing. I think that if luminol evidence is so questionable, it should not be used at any crime scene ... yet it is. I suppose that means that luminol evidence is quite valuable.
It has value, it just isn't the "gotcha" that it is portrayed to be in crime shows. This is because so many substances--including bleach, for God's sake--glow in response to luminol.
Finding a resident's footprints with luminol in her own home doesn't really tell us much.