A federal appeals court in Chicago ruled on Wednesday that police did not violate a suspect's constitutional rights when they searched his cellphone without a warrant.

In the decision, Judge Richard Posner noted that the case has implications for whether police can search computers without a warrant because modern cellphones essentially are computers.

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In the case, Indiana police arrested Abel Flores-Lopez, a suspected drug dealer, and seized his cellphone. Without a warrant, they used his phone to discover its number, and then used the number to subpoena call records from his telephone company.

Prosecutors used the call records as evidence to convict Flores-Lopez on drug charges. His lawyers argued that the records should have been excluded from the trial because the search violated his Fourth Amendment right to be protected from "unreasonable searches and seizures."

But the three-judge panel of the 7th Circuit Court of Appeals disagreed, ruling that using a phone to discover its number is not invasive enough to require a search warrant.

Posner acknowledged that cellphones can contain deeply personal information, but he said police only searched the phone for its number, which he called a "modest cost in invasion of privacy."

He compared the search to seizing a diary to verify the person's name and address.

"If police are entitled to open a pocket diary to copy the owner’s address, they should be entitled to turn on a cell phone to learn its number," Posner wrote.

He added that if police are banned from reading love letters wedged between the pages of an address book, they should also be banned from reading love messages in a phone.

He noted that police could have discovered the phone number in two clicks if it was an iPhone and one click if it was a Blackberry (the trial court never specified the model of the phone).

"We are quite a distance from the use of the iCam to view what is happening in the bedroom of the owner of the seized cell phone," Posner wrote.