Italy is known to have a dysfunctional judicial system, and there are many miscarriages of justice; the Knox - Sollecito trials were not unique that way. Of course, the PGP ignore these issues to pretend that the Massei and Nencini courts, which convicted Knox and Sollecito, and the Chieffi CSC panel, which quashed the Hellmann court's acquittal of them, were perfect. On the other hand, the PGP claim that there was some underhand or illegal manipulation that resulted in the acquittal by the Hellmann court and the final and definitive acquittal by the Marasca CSC panel; the PGP ignore the valid criticisms of the Hellmann court of the Masse court verdict and of the Marasca CSC panel of the Nencini court verdict.
Here's an excerpt from an article discussing some issues in the Italian judicial system:
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Slow-moving, hugely bloated and sometimes alarmingly politicised, Italy's justice system needs fixing. In a critical report last year, the Council of Europe's top official for human rights, Nils Muiznieks, said Italy could "ill-afford" such an inefficient system, which is estimated to waste the equivalent of 1% of GDP. "The complexity and magnitude of the problem is such that Italy needs nothing short of a holistic rethinking of its judicial and procedural system, as well as a shift in judicial culture," he wrote of the country's "excessive" court proceedings.
Paula Severino, the justice minister under Mario Monti, attempted to improve the situation by pushing through reforms and cuts she estimated would make savings of €80m and improve efficiency. But she warned that, just as Rome wasn't built in a day, a system that was the product of 150 years of mismanagement and waste was not going to be put right in the short term of a technocratic government.
Italy is one of the most litigious countries in Europe, with more than 2.8m cases brought in 2011 alone, and has by far the most lawyers of any EU country – around 240,000. But the system simply cannot cope. Last year Severino said there were backlogs of 5.5m civil and 3.4m criminal cases waiting to be heard, with the former taking an average of seven to eight years to complete and the latter five. The system is clogged up with a vast number of appeals – Italy's top appeals court reviews more than 80,000 of them a year – and,
in 2011, €84m was paid out by the state in compensation for miscarriages of justice and legal delays, along with €46m for people wrongly jailed.
A shockingly high proportion of inmates in Italy's overcrowded prisons are awaiting trial. Meanwhile, others remain free pending appeals against lower court convictions. Berlusconi, for instance, was convicted of tax fraud last year. He is appealing against the verdict and is campaigning for a fourth election victory. Often, by the time defendants have completed the two appeals to which they are entitled, the statute of limitations has expired and the slate is wiped clean."
Source:
https://www.theguardian.com/world/2013/feb/20/six-things-wrong-with-italy