The issue doesn't really matter in cases where the raw files were not requested, were produced, or it can be shown that either the data or the DNA results don't really matter.
I'm guessing that there are very few cases where access to EDFs was requested and so strongly resisted by the authorities, and the DNA results were so shaky and yet decisive. This may be a bellwhether case in Italy.
Note, though, that the RIS attached their underlying data to their report to Nencini without any fuss. Also, Novelli was readily given access to not only lab results from this case, but also from other cases, simply by asking, and contrast that to the way the authorities responded to the defendants requests.
I would imagine that the number of innocent people wrongly convicted in Italy on the basis of forensic evidence presented at trial by the prosecution where full disclosure was not made and who are currently in jail, is significantly greater than zero, though I agree that there will be numerous cases where the non-disclosure of data had no bearing on the result at trial. A problem would be that the value of the data to the defence may not be known until it is examined by an expert. But given Stefanoni's denial of contamination events in her lab and the courts' ready acceptance of her claims, I can only presume that problems are not limited to the present case.
All we appear to know is, if Stefanoni is being truthful, Polizia Scientifica has never disclosed data to defences in any case it has handled. I wonder how many cases that is? We do not know for certain however, how desperate the situation is elsewhere in Italy (although Stefanoni says the data is never disclosed anywhere) - in how many cases disclosure of data was made without request, with request or in how many cases it would or should have made a difference at trial. As you correctly point out, in this case we have one instance of testing from the carabinieri lab where the data was provided, in sharp contrast to Stefanoni's lab where the prosecution consultant was given exclusive access to evidence. So, is this more likely to be exclusively a Polizia Scientifica problem? Perhaps so.
In cases where the raw data was not disclosed, that could be enough, with other trial matters, to be regarded as a breach of a defendant's convention rights under Article 6(3)b taken together with the equality of arms principle. Of course, whatever cases there are, are out of time with regard to applications to the ECHR, (other than those with finalised convictions in the last six months), yet Convention law still applies and overrides ordinary law in Italy.
It might be difficult and ultimately expensive, but lawyers, even where requests had not been made at trial, could try raising in the Italian courts, among others, the old case, Jespers v Belgium, which is still offered by the European court in advisory documents as a basis for upholding rights of discovery, ("....imposes an obligation on prosecuting and investigating authorities
to disclose any material in their possession, or to which they could gain access, which may assist the accused in exonerating himself or in obtaining a reduction in sentence.") perhaps as part of an appeal for a Review of Trial or perhaps they might even attempt to use the modified art 630 to force a re-trial instead.
If the Knox/Sollecito murder convictions go to the ECHR and it rules specifically on DNA discovery, that would create a better gateway - as you say, a bellwether case.
Perhaps in future, the ECHR might, if alerted to the problem in Italy with discovery, adopt a pilot judgement procedure.
"....developed as a technique of identifying the structural problems underlying repetitive cases against many countries and imposing an obligation on States to address those problems. Where the Court receives several applications that share a root cause, it can select one or more for priority treatment under the pilot procedure. In a pilot judgment, the Court’s task is not only to decide whether a violation of the European Convention on Human Rights occurred in the specific case but also to identify the systemic problem and to give the Government clear indications of the type of remedial measures needed to resolve it."
Of course, this would require defence lawyers in relevant cases to understand the rights of their clients and to follow through with applications to the ECHR.
It seems to me, however, as a minimum, that a proactive review of at least a healthy random sample of Polizia Scientifica cases, should take place. I wonder if the Justice Ministry or similar has the power to order that?