and just ask that it be kept under wraps until we can get him secured. i mean, we negotiated that. it was like, listen, don't get me involved in this. i want to do this for the family. this guy's dangerous. so until you get handcuffs on him, you can't involve me." >> reporter: but evans knew, even if he did arrest the guy, a mystery woman testifying about something an ex-boyfriend told her wouldn't be enough. >> i can imagine a prosecutor saying, well, i can't just put her on the stand, his attorney will come along and say, "she's full of it." >> yeah, and in this particular case it's, yeah. you know what? that in itself is not gonna do it, nor should it. we're still in a situation where this has to come from him. >> reporter: him, meaning shane ragland. evans told her they had to find a way to get shane to admit on tape what he did, otherwise what jury would buy such a ludicrous motive for murder? there was only one way, he told her, she'd have to wear a wire.