Well, even if such a test ever proved to be fruitful (which is unlikely now), that still wouldn't mean Jeremy didn't kill the family. I don't believe the silencer was used, but I STILL believe he's guilty.
However, IF this were ever proved, I do believe that he would deserve a retrial but NOT that he should walk from the COA a free man. (Although I don't believe either will ever happen).
Caroline, artefacts recovered from prehistorical site digs can still produce human DNA, so there is a very good chance that hidden away and concealed in the voids of the aforementioned rifling inside the rifle barrel, will produce DNA of the victims, if the silencer was not used! It doesn't matter how long it has been in the lifetime of this case thus far, if the DNA of victims is there in any of the rifling voids of the guns barrel, it could only have got there without the silencer having been attached to the barrel. The silencer has already been tested to death and the gist of the evidence obtained from various examinations of it, suggested that it was Sheila's blood found inside the silencer as far down as the fifth or sixth baffles of seventeen in total! There was a possibility that the blood might be a mixture of the parents bloods! However, between the sixth and seventeenth baffle plate, there was no blood whatsoever, a gap which cannot be ignored should victims blood and or DNA be recovered from the recessed voids of the rifling inside the guns barrel by way of the Keith Mallinson proposal!
That 'Gap' consisting of eleven or twelve perfectly clean and uncontaminated baffle plates at the bottom end of the silencer would not sit well with a presence of victims blood, and or DNA in the aforementioned recesses of the rifling voids of the guns barrel as alluded to by the Mallinson theory!
I fear that the net result would be that the prosecution would have to finally concede that Jeremy Bamber had been wrongly convicted of the murders by the introduction of a dodgy silencer which someone had deliberately contaminated with blood and paint for the sole purpose of establishing that Sheila Caffell could not have committed suicide with use of that gun minus it's silencer, because during the trial the blood expert claimed that the blood found inside that silencer was in his view, unique and exclusive to her...
Yet, none of Sheila Caffells DNA was found to be present inside the silencer as per the 2002 test results. It is irrelevant that the court of appeal stated that the DNA evidence in that appeal could have got there as a result of cross contamination, since whether that be true or not, had Sheila Caffells DNA been present there inside that silencer it should have been detectable in any event, as evidenced by the fact that at least three different or separate DNA profiles were detected in the tests carried out in 2001 / 2002...
As far as I am aware, unlike where blood from two victims can mix intimately, or mask one blood group by another, this does not apply when dealing with DNA, which are uniquely distinguishable from one another!