The lead detective has been sent to Apple's headquarters in California as he tries to obtain messages sent from the phone of the Olympic and Paralympic star in and around the time he shot to death his girlfriend Reeva Steenkamp on Valentine's Day 2013.
The matter has taken on even greater urgency as Pistorius's trial is due to begin in Pretoria on Monday
The 27-year-old Pistorius, nicknamed the Blade Runner, denies murder and claims that he shot Steenkamp accidentally, believing she was an intruder in his home in Pretoria.
After the shooting, police obtained Pistorius' iPhone but have been unable to access his 'iCloud account' which could contain a digital footprint of deleted text messages, emails and other exchanges between him and Steenkamp.
The police have not been able to access the phone's details because they keep getting the message: 'Your Apple ID or password is incorrect!'
Pistorius’ legal team insist they passed on the correct password for the account but the police have not been able to access the account and legal red tape means they need to travel to America to try and get Apple to grant them access.
South African newspaper City Press reports: "Apple experts say there are two reasons a password could be wrong: either the phone’s owner remotely changed the password or the owner opened a new account, in which case the new password would not correspond with the Apple ID on the phone.
"Investigators will probe whether the password was changed or a new account was set up. But for now they are battling intercontinental red tape.
"Police (in South Africa) need a US court to instruct Apple to crack the code to Pistorius’ iPhone. The International Cooperation in Criminal Matters Act has been used for this. Police have the relevant documents from courts at home and have, through the South African embassy in the US, asked the FBI for help.
"One member of the prosecuting team says the process has become 'a logistical and bureaucratic nightmare because US privacy laws are a lot tougher than those in South Africa'."
Nathi Mncube, a spokesman for the National Prosecuting Authority, confirmed the US trip.
"We have sent officials who are meeting with Apple today with the purpose of unlocking an iPhone. We followed the mutual legal assistance processes.
"With or without this evidence, the trial will still continue on Monday and we feel that we have more than enough evidence regardless, but any evidence we can lay our hands on is critical."
The case will last two weeks and is expected to hear evidence from more than 100 witnesses.
Pistorius is charged with premeditated murder, illegal possession of ammunition, as well as two additional gun-related charges.
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