—the Supreme Court held that "a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties."

"[T] he application of the Fourth Amendment depends on whether the person invoking its protection can claim a `justifiable,'a `reasonable,'or a `legitimate expectation of privacy'that has been invaded by government action. "

—holding, in the context of telephonic technology, that defendant had no expectation of privacy in pen register listing phone numbers dialed from his phone

The second question is whether the individual's subjective expectation of privacy is "one that society is prepared to recognize as `reasonable,'"—whether... the individual's expectation, viewed objectively, is" justifiable "under the circumstances.

—the Supreme Court held individuals have no "legitimate expectation of privacy" regarding the telephone numbers they dial because they knowingly give that information to telephone companies when they dial a number.

The Court held that the defendant could "claim no legitimate expectation of privacy" in the numbers he had dialed because he had "voluntarily conveyed" those numbers to the phone company by " `expos [ing]'that information to "the phone company's" equipment in the ordinary course of business. "

Because the Taxpayers have no Fourth Amendment right at stake, the IRS need not obtain a warrant supported by probable cause to get the records.

We have applied this test in holding that it is not a search for the police to use a pen register at the phone company to determine what numbers were dialed in a private home

—decided in 1979, the Supreme Court held that the installation of a pen register was not a search within the Fourth Amendment.