Comey said Wednesday night that the FBI used a tool to unlock the phone, which is provided by a third party who was not identified, will not work on newer models of iPhone, such as 5s, 6 or 6s.
FBI ended high-profile legal battle with Apple when it acquired the technology and access the phone is concerned, but that leaves a legal issue that is greater than the overall iPhone encryption and privacy unresolved.
The FBI is already facing the prospect of again asking for help cracking Apple iPhone connected to the case. The Justice Department has asked a New York court to force Apple to open an iPhone 5s involved in drug investigations.
Prosecutors in the case that would allow the court know April 11 whether to ask help from Apple, but in doing so, the government could give the company the opportunity to force the FBI to reveal the secret technology, claiming legal discovery, a source close to the situation told Reuters news agency.
If the FBI said Apple defect regarding encryption exploited to gain access to the phone, "then they will fix it and we're back to the starting point from," said Comey spectators Kenyon College in Gambier, Ohio.
The iPhone is owned by Syed Farook who, along with his wife, killing 14 people in San Bernardino in December.
