Just like local police departments, state troopers have their own investigative divisions to solve crimes. Some states have separate bureaus of investigation for this, while others have detective ranks built into the state police department.
The criminal investigations at state police agencies may concentrate on some of the same people who are under local police departments' radar. But the state police investigations often have a broader scope. These investigations may cover felons who have committed a series of crimes across the state, drug lords or suspected terrorists. State troopers may also collaborate with local and federal officers as well, depending on the case.
One of the main reasons that state police were formed was to prevent criminals from skipping over county lines to escape punishment. State police, however, can step in to capture at-large criminals in the state, regardless of the local jurisdiction. This happens when felony suspects or high-profile criminals that federal authorities are looking for are on the loose. Also, the state troopers' role in policing rural areas that don't have their own law enforcement agencies helps keep criminals from using those areas as hiding places.
Illegal drugs are a major concern of state criminal investigations units. The state may form a drug task force, or special investigative project, with local departments in areas known to have high drug activity. From 1980 to 2006, the number of drug-related arrests in the United State skyrocketed more than 300 percent [source: Bureau of Justice Statistics]. Specially trained state troopers may go undercover through a sting operation to catch dealers or manufacturers. Many state agencies even have helicopters with heat sensors that can detect where marijuana may be growing in houses.
To reduce the violent crime rate, state police also try to halt illegal gun trafficking. Gun trafficking happens when firearms are sold to people who aren't authorized to own them. According to the Illinois State Police, more than 90 percent of guns used in crimes are trafficked [source: Illinois State Police Department]. State police can pinpoint drug trafficking activity by analyzing data from gun-related crime to track down the source of the guns. State police may also work with federal agencies such as the Bureau of Alcohol, Firearms and Tobacco and local police departments to catch traffickers.
Since September 11, 2001, the federal government has heavily funded counterterrorism efforts in state police departments. The Department of Homeland Security doled out more than $500 million to states in counterterrorism grants for the 2007 fiscal year [source: Department of Homeland Security]. This funding goes toward training for terrorism attack response, monitoring terrorism activity in the state and capturing information related to state and national terrorism activity.
In recent years, public attention has increasingly shifted toward illegal immigration. Since immigration is a federal issue, state police have no authority to arrest people they suspect are in the United States illegally. However, there have been efforts to change that, particularly in Massachusetts. There, former governor and unsuccessful Republican presidential candidate Mitt Romney brokered a deal to allow a select number of state police to detain suspected illegal immigrants [source: Levenson and Saltzman]. Missouri is also among other states that have recently granted this power to state police officers.
When major criminal investigations arise, special units are sometimes called. We'll explore the most common special units on the next page.