I disagree entirely. Perhaps the system is different in the US but the UK system simply requires some fresh evidence that had the jury known about at trial might have caused them to return a different verdict. It's absolutely not necessary to take apart all or any of the prosecutions case at trial. Why would SC's fingerprints be on the casings if she hadn't loaded them into the mag?
Fingerprints are stronger evidence than DNA. Fingerprints alone are enough for a conviction whereas DNA requires further supporting evidence.
All fingerprints can prove is that she handled ammunition at some point in time not that she loaded it into the weapon let alone fired the weapon. The conviction was based upon evidence that she did not load the gun did not fire the gun did not beat Nevill and could not have killed herself as well as Julie's testimony that Jeremy did it and framed Sheila. The main evidence presented at trial was:
1) that if she loaded the ammunition in the magazine she would have had visible deposit on her hands and elevated lead levels would have been detected
2) that if she fired the weapon GSR would have been found
3) that if she beat Nevill his spatter would have gotten on her
4) that it was not possible for her to have killed herself
5) that prior to the murders Jeremy plotted to kill them and to frame Sheila and admitted afterwards to Julie that he was responsible
While you choose to believe that fingerprints on the casings is a game changer and refutes the above the reality is that it does not and the Court of Appeals would not find it a basis upon which to vacate the conviction.
The only major difference between the US and UK on appeals based on new evidence is procedural. In the US there is no body like the CCRC to go through an appeal is filed directly with a court. In state actions it will usually be filed with the original trial court subject to appeal to an intermediate level appeal court and then the highest state court. When such is exhausted an action for Habeas corpus can be filed in the federal courts as well depending on the facts. In a federal case it will go to an appeals court and can be appealed to the US Supreme Court. The US Supreme Court and highest court in each state don't have to hear such appeals they decide whether to hear the appeal or simply let the lower decision stand without hearing it. So in the US there are much more layers of court action and more opportunities to try appealing. This is why cases last so long they can bounce around among appeals courts for a long time. A favorite argument for a new trial is saying the trial counsel was ineffective. The theory is that it was not a fair trial because the trial counsel did such a poor job below the acceptable standards. That is much more commonly used to try to secure an appeal than other grounds.
In both the US and UK if evidence got before the jury that should not have either because it was not legally admissible and the judge screwed up in admitting it or because the person admits they lied the conviction will be vacated ONLY IF the court decides that a reasonable person could have convicted on the basis of such evidence that should not have been before the jury. If they could not have convicted on such basis it is harmless error. Sometimes it is hard assess whether testimony is so damning as to warrant a reversal. Here it is not, the judge expressly told the jury they could convict solely on her testimony if they believed it. It's not a close call quite clearly if she lied that warrants a reversal even though the other evidence is still enough to convict because they might have convicted in part or whole on the basis of her explosive testimony.
In both the US and UK new evidence has to be of such a nature that it results in proving innocence or at the very least the new evidence must be sufficient that a reasonable juror could acquit on the basis of such evidence. In order for evidence to have the ability to cause a reasonable person to acquit it must undermine the evidence that formed the basis of the conviction.
Evidence Sheila touched the ammunition at some point in the past fails to establish she loaded the weapon, fired the weapon and could have killed herself. It doesn't undermine any of the following prosecution arguments:
1) that if she loaded the ammunition in the magazine she would have had visible deposit on her hands and elevated lead levels would have been detected
2) that if she fired the weapon GSR would have been found
3) that if she beat Nevill his spatter would have gotten on her
4) that it was not possible for her to have killed herself
5) that prior to the murders Jeremy plotted to kill them and to frame Sheila and admitted afterwards to Julie that he was responsible
Evidence has to undermine several of these not just 1 in order to rise to a level sufficient to support an acquittal and fingerprints on casings would not even undermine 1 of them.
The only ones capable individually of warranting vacating the conviction would be to establish Julie lied (for the reasons mentioned above) or evidence that she could not have killed herself because each of these individually were so significant in terms of the overall case.