Ms Knox, now 31, was convicted but later cleared of murdering 21-year-old Meredith Kercher in Italy in 2007.
She was released from prison after serving almost four years – but her conviction for malicious accusation was upheld.
The European Court of Human Rights (ECHR) said on Thursday that there had been breaches of Ms Knox’s rights leading up to the remaining conviction.
Italian police alleged Ms Knox made false accusations against Congolese bar owner Diya “Patrick” Lumumba, knowing him to be innocent and in order to distract investigators away from her own responsibility.
However Ms Knox appealed on the grounds she was denied access to a lawyer and an independent interpreter, and was slapped on the head and subjected to psychological pressure when interviewed by Italian police.
The ECHR ruled that there had been a violation of Ms Knox’s rights when her claims of ill-treatment in police custody were not investigated – although judges said the court had not seen any evidence of the “inhuman or degrading treatment” she complained about.
They also said the Italian government had failed to show that Ms Knox’s restricted access to a lawyer during the police interview had not “irreparably undermined the fairness of the proceedings as a whole”.
Judges further found that authorities had failed to assess the conduct of the interpreter assigned to Ms Knox and whether this had affected criminal proceedings against her.
The Italian government was ordered to pay Ms Knox €10,400 (£9,000) in damages and €8,000 (£7,000) for costs and expenses.
The judges’ ruling is not yet final, with any party in the case given a three-month period to request for it to be referred to the Grand Chamber of the ECHR, where it could be further examined.
The body of Meredith Kercher, a 21-year-old British exchange student, was found by police in the flat she shared with Ms Knox in Perugia, Italy, on 2 November, 2007.
Officers discovered her throat had been slashed and that she had been sexually assaulted.
Ms Knox and her then-Italian boyfriend Raffaele Sollecito were found guilty of murder and sexual assault, but their convictions were later overturned.
Two years later, the Perugia Court of Appeal acquitted the pair of the more serious charges, but upheld Ms Knox’s conviction for malicious accusation.
Ms Knox challenged the malicious conviction, but the Court of Cassation – the country’s highest court – quashed her acquittal in 2013 and referred the case back to the Assize Court of Appeal.
That court re-sentenced her to more than 28 years in prison for complicity in sexual assault and murder, and three years for malicious accusation.
Ms Knox launched another appeal, and in 2015 she and Mr Sollecito were acquitted of sexual assault and murder by Italy’s highest court, but Ms Knox was not cleared of the malicious accusation charge.
Rudy Hermann Guede, from the Côte d’Ivoire, is serving a 16-year sentence for Ms Kercher’s murder.
Press Association contributed to this report
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