Wow, interesting! Chain of custody would have to be a big problem if the bootlace was to be used as evidence to convict A.N. Other, however if it did point to someone more plausible than Stone, I think it very much should be used to support his case, which already has merit in my opinion. We already had the towel strips with DNA components from an unknown male (Not Stone, nor the husband/father), if the bootlace should also produce unrelated DNA, then that adds a big forensic argument in his favour, particularly if it ties in with the partial profile from the towel.
It'll be very interesting indeed to see what follows from this, I hope it supplies some evidence to clarify things one way or another, as it's a case that makes a few of us very uneasy, judging by posts I read here.