If the police believe a computer is itself evidence of a crime — for example, if it is stolen or was used to commit a crime — they will usually seize it and then search its contents later. However, if the evidence is just stored on the computer — for example, you have computer records that contain information about the person they are investigating — instead of seizing the whole machine, the police may choose to:
Search the computer and print out a hard copy of the particular files they are looking for (this is rarely done)
Search the computer and make an electronic copy of the particular files
Create a duplicate electronic copy of all of the computer's contents (this is called 'imaging' or creating a 'bitstream copy' of the computer hard drive) and then search for the particular files later
'Sneak and Peek' Search Warrants Are Easier to Obtain Than They Used to Be
Generally, police officers serving a warrant must 'knock and announce' — that is, give you notice that they are the police and are serving a warrant (although they might not do this if they reasonably suspect that they will be put in danger, or that evidence will be destroyed, if they give such notice). If they have a warrant, they can enter and search even if you aren't home — but they still have to leave a copy of the warrant and an inventory of what they seized, so you'll know that your place was searched.
However, thanks to the USA PATRIOT Act, it is much easier for law enforcement to get permission from the court to delay notice rather than immediately inform the person whose premises are searched, if agents claim that giving notice would disrupt the investigation. Since the goal is not to tip the suspect off, these orders usually don't authorize the government to actually seize any property — but that won't stop them from poking around your computers.
The delay of notice in criminal cases can last months. The average delay is 30 to 90 days. In the case of super-secret foreign intelligence surveillance to be discussed later, the delay lasts forever — no one is ever notified, unless and until evidence from the search is introduced in open court.
The risk of being targeted with such a 'sneak-and-peek' warrant is very low, although rising quickly. Law enforcement made 47 sneak-and-peek searches nationwide from September 2001 to April 2003 and an additional 108 through January 2005, averaging about fifty per year, mostly in drug cases. We don't know how many foreign intelligence searches there are per year — it's secret, of course — but we'd guess that it's much more common than secret searches by regular law enforcement.
Secret searches can be used to install eavesdropping and wiretapping devices. Secret searches may also be used to install a key-logging device on your computer. A key-logger records all of the keystrokes that you make on the computer's keyboard, for later retrieval by the police who installed it. So if you are concerned about government surveillance, you should check your office computers for new added hardware that you don't recognize — especially anything installed between the keyboard and the computer — and remove it. A hardware key-logger often looks like a little dongle in between the keyboard plug and computer itself. Keyghost is an example of a hardware key-logger.
However, the government also has the capability to remotely install software key-loggers on your computer — or search the contents of your hard drive, or install surveillance capability on your computer — using its own spyware. There were rumors of such capability a few years ago in news reports about a government software program code-named “Magic Lantern” that could be secretly installed and monitored over the Internet, without the police ever having to enter your house or office. More recently, news reports revealed that the government had in one case been able to hack into a computer remotely and install software code-named “CIPAV” (the 'Computer and Internet Protocol Address Verifier'), which gave the government the IP addresses with which the infected computer communicated.
In response to a survey, all of the major anti-spyware companies claimed that their products would treat government spyware like any other spyware programs, so you should definitely use some anti-spyware product to monitor your computer for such programs. It's possible that a spyware company may receive a court order requiring it not to alert you to the presence of government spyware (several of the companies that were surveyed declined to say whether they had received such orders), but you should still use anti-spyware software if only to protect yourself against garden-variety spyware deployed by identity thieves and commercial data harvesters.
There Are Many Fourth Amendment Exceptions to the General Rule of Warrants
In some cases, a search can be reasonable — and thus allowed under the Fourth Amendment — even if the police don't have a warrant. There are several key exceptions to the warrant requirement that you should be aware of.
Consent. The police can conduct a warrantless search if you voluntarily consent to the search — that is, if you say it's OK. In fact, any person who the police reasonably think has a right to use or occupy the property, like a roommate or guest in your home, or a coworker at your office, can consent to the search. You can make clear to the people you share a home or office with that they do not have your permission to consent to a search and that if police ask, they should say no.
Privacy tip: Don't accidentally consent!
If the police show up at your door without a warrant, step outside then close and lock the door behind you — if you don't, they might just walk in, and later argue that you implied an invitation by leaving the door open. If they ask to come in, tell them 'I do not consent to a search.' Tell roommates, guests, coworkers and renters that they cannot consent on your behalf.
Administrative searches. In some cases, the government can conduct administrative searches. These are searches done for purposes other than law enforcement; for example, for a fire inspection. Court authorization is required for involuntary administrative searches, although the standards are lower. The only time the government doesn't need a warrant for an administrative search is when they are searching businesses in highly regulated industries such as liquor, guns, strip mining, waste management, nuclear power, etc. This exception to the warrant requirement clearly does not apply to the average homeowner, activist organization or community group.
Privacy tip: Just because they're 'inspectors' doesn't mean you have to let them in!
If someone shows up at your home or office claiming to be a fire inspector, building code inspector, or some other non-law enforcement government employee who wants to inspect the premises, you can tell them to come back with a warrant. You don't have to let them in without a warrant!
Exigent circumstances. Exigent circumstances are emergency situations where it would be unreasonable for the police to wait to get a warrant, like if a person is calling for help from inside your house, if the police are chasing a criminal suspect who runs into an office or home, or if evidence will be destroyed if the police do not act immediately.
Privacy tip: Don't get tricked into consenting!
Police could try to get your consent by pressuring you, or making you think that you have to let them in. For example, they may show up at your door claiming that your neighbor saw someone breaking into your home or office, saw a criminal suspect entering the premises, or heard calls for help, and that they need to take a look around. You should never physically interfere if they demand to come in (which they will do if there are indeed exigent circumstances), but no matter what they say or do, keep saying the magic words: 'I do not consent to a search.'
Plain view. The police can make a warrantless search or seizure if they are lawfully in a position to see and access the evidence, so long as that evidence is obviously incriminating. For example, if the police enter a house with a valid search warrant to search for and seize some stolen electronics and then see a bag of drugs in plain view on the coffee table, they can seize the drugs too, even though the warrant didn't specifically authorize that seizure. Similarly, the police could seize the drugs without a warrant, or look at any other documents or things left in plain view in the house, if there were exigent circumstances that led the police into the house — for example, if a suspect they were chasing ran into the house, or if they heard gunshots from inside. Even a law- abiding citizen who does not have any contraband or evidence that the police would want to seize may still have sensitive documents in plain view that one would not want the authorities to see.
The plain view exception alone does not allow the police to enter your home or office without a warrant. So, for example, even if the police see evidence through your window, they cannot enter and seize it. However, plain view can combine with other exceptions to allow searches that might otherwise require a warrant. For example, if the person with the bag of drugs in the previous example saw the police looking through his window,
