Top prosecutor Alison Saunders has said she does not think anyone is in jail after being wrongly convicted because of failures to disclose crucial evidence.
The head of the Crown Prosecution Service insisted the justice system is working despite a string of trial collapses.
Scotland Yard launched an urgent review of around 30 sex cases due to go to trial after the collapse of two rape prosecutions in a week in December.
The Director of Public Prosecutions (DPP) is meeting senior police officers and barristers on Thursday to discuss concerns that vital material is not being disclosed.
Asked if it was possible there were people in prison today because of disclosure failures, Ms Saunders replied: "I don't think so because what these cases show is that when we take a case through to trial there are various safeguards in place, not least of which the defence indicating what their defence is going to be."
She told BBC Radio 4's Today programme: "The problem we have found recently is around the ever-increasing use of social media, all the digital material we obtain."
Ms Saunders suggested photographs and social media accounts do not need to be fully checked in rape cases.
Police are obligated to pursue "all reasonable lines of inquiry", she said.
"That doesn't mean going into every single avenue of your life."
The trial of Liam Allan, 22, was halted at Croydon Crown Court in December while days later another prosecution collapsed against Isaac Itiary, who was facing trial at Inner London Crown Court accused of raping a child.
Both cases involved the same investigating officer, and the detective remains on full duty in the sexual offences investigation unit, the Metropolitan Police said.
A third rape trial collapsed after a failure from investigators to find key evidence on Monday.
The case against Samson Makele was halted at Snaresbrook Crown Court on Monday after his defence team unearthed key images from his mobile phone which had not previously been made available, law firm Hodge Jones and Allen said.
The 28-year-old was accused of raping a woman he met after the Notting Hill Carnival in 2016 but the case, due to go to trial at the end of the month, was thrown out after more than a dozen pictures emerged of the pair apparently cuddling in bed.
Mr Makele, originally from Eritrea, claimed the sex was consensual.
Investigators from the Metropolitan Police did not find the images, which were discovered when the defence hired an independent forensic expert.
On Mr Makele's case, the DPP said: "How would anyone have known that there were photographs there until the defence had told us that they were there?"
She added: "The system worked. What I think should have happened in that case is it should have happened much earlier."
Conservative MP Anna Soubry said she feared Mrs Saunders was "part of the problem".
"Appalled at the ill informed comments of #DPP Alison Saunders," she tweeted. "There hv been longstanding problems w disclosure."