It took less than a week for law enforcement to identify two suspects in the Boston Marathon bombing.

Once the FBI released photos and video of Tamerlan Tsarnaev, 26, and Dzhokhar Tsarnaev, 19, who police believed had carried out the bombing that killed three people and severely injured many others, Boston-area police officers were conducting door-to-door searches of homes in several Boston neighborhoods looking for the younger suspect, Dzhokhar.

The Fourth Amendment protects citizens from unreasonable searches and seizures. No place receives more protection than the home. Generally, police officers are required to “knock and announce” their presence before entering and obtain a search warrant before conducting a search.

However, there are several exceptions that allow police to conduct a search without first obtaining a warrant. One such exception came into play during the manhunt for one of the Boston Marathon bombing suspects—exigent circumstances or emergencies.

The exigent circumstances exception allows police officers to enter, search, or seize a person’s property without a warrant. Generally, this exception applies when police are in hot pursuit of a known suspect,when further harm or injury could result in the time it would take to get a warrant, or other emergencies requiring a quick response.

The reason for this exception is self-explanatory. It would be difficult, if not impossible, to efficiently conduct a manhunt for a potentially dangerous suspect, as the case was with the Boston Marathon bombing suspect, if police would have had to obtain a warrant for each house they wanted to search.

After hours of door-to-door searches, Boston-area police apprehended Dzhokhar, who had secreted himself in a boat on the property of an unsuspecting home owner.