Law enforcement officers use a mail cover to gather intelligence regarding suspects. They can receive special permission from the US Postal Inspection Service to record information from the outside of sealed or unsealed mail. Use of this technique is strictly regulated by federal law. Only the Chief Postal Inspector or that person’s designee can authorize a mail cover. Any interference with mail by law enforcement or anyone else is a federal offense.
No one besides sanctioned law enforcement agencies may request a mail cover. Postal employees are the only ones allowed to record the information, which can then be passed to the inquiring party. Investigators must make a request in writing to the Postal Inspection office. In the case of an emergency situation, a local postal inspector can grant verbal permission, or the office can do so pending receipt of a formal request within three days of the operation. The request does not authorize law enforcement to seize or open mail without a federal search warrant or a legal exception to that warrant.
Investigators asking for a mail cover need to fill out certain forms. The information on the application includes, but is not limited to, the length of time the cover is needed, the reasons why it is being requested, the name and address of the subject, and how it will be used to develop evidence. Mail covers cannot be used in as evidence, only for generating leads, and is not a routine investigative step. The US Postal Service strongly discourages investigators not to disclose when they are using this technique.
Interference with the mail is a federal crime, punishable by US law. Other than authorized personnel, such as a secretary or mail clerk, anyone opening another person’s correspondence or recording information from it may be subject to federal prosecution, fines, or even jail time. Postal employees can be charged for telling a person that his mail is being monitored, according to a federal law prohibiting the release of confidential government information.
Some people have argued that the use of a mail cover violates a person’s Fourth Amendment rights against unreasonable search and seizure. US courts have upheld that it does not, on the grounds that there is no reasonable expectation of privacy from employees of public utilities or agencies when sending information through those entities. Along with pen registers, wiretaps, and other tactics, a mail cover is merely a tool employed by law enforcement to supplement solid investigative work.