Located within the Investigative Services Bureau, the Major Crime Unit was created out of the necessity for highly trained, task-specific investigators assigned to handle the most egregious and sensitive offenses. The Unit's primary responsibility is homicide investigation.  Unit members are assigned in seven sections responsible for specific aspects of major investigations, including Crime Scene Services, Cyber Crime, Historic Cases, Missing Persons, Polygraph, ViCAP, and Corrections Liaison.

Crime Scene Services provides a coordinated response to the various crime scenes that are encountered throughout the state by State Police, as well as local, county and federal law enforcement agencies. Crime Scene Services is comprised of members of the Major Crime Unit who are experienced and trained to locate, identify, document and collect physical evidence associated with the scene of a crime. Crime Scene Services is frequently called to assist in the reconstruction of critical events to bring an investigation to its logical conclusion.

While the campaign to combat the exploitation of children is the primary focus, the Cyber Crime Section has seen significant increases in all types of computer and internet-related crime. In addition to child exploitation cases, investigators conduct investigations involving alleged hacking, on-line harassment, and on-line fraud. Given the current state of computers in modern society, the Cyber Crime Section provides on-scene inspection and forensic analysis working in partnership with the Forensic Laboratory and law enforcement agencies throughout New Hampshire.

The Division of State Police founded the Historic Case Section in 1994 to focus investigative efforts on unsolved homicides under investigation. During an investigator’s methodical review, the case information is organized and examined for new avenues of investigation, including the latest advances in the field of forensic science. The Historic Case Section routinely reviews investigative leads and intelligence received on unsolved cases from law enforcement agencies and citizens for possible connection to homicides under investigation. The Historic Case Section also interacts with numerous criminal intelligence networks throughout the country in order to maximize the potential for solving cases and to assist other law enforcement agencies in solving cases within their jurisdictions.

The Missing Persons Section is responsible for investigating missing and unidentified persons. The Missing Persons Section also maintains the State Clearinghouse for Missing and Exploited Children. The Clearinghouse is responsible for tracking all of New Hampshire’s missing person cases, dental record entry, and offers technical assistance with photo and flyer creation and distribution.

For over 30 years the New Hampshire State Police Polygraph Section has offered forensic polygraph support to law enforcement. The Polygraph Section is comprised of expertly trained and certified Forensic Polygraph Examiners. The Polygraph Section provides the equipment and environment for a useful work product affirming or dispelling investigative issues.

The New Hampshire State Police is currently the in-state clearinghouse for ViCAP (Violent Criminal Apprehension Program). The Federal Bureau of Investigation administers ViCAP nationally. ViCAP entails the collection and analysis of case information on homicides, other violent criminal cases, and missing persons cases with suspicious circumstances. ViCAP reports are entered in the New Hampshire database and then electronically transmitted to the FBI ViCAP Unit, where they are entered into, and queried against, the national database. When possible links are found, the submitting agencies are put in contact with each other for follow-up investigation.

The mission of the Correctional Liaison Section is to investigate crime and coordinate intelligence within the state’s correctional institutions. These institutions include the Men and Women's prisons, the Lakes Region facility, the North Country facility in Berlin and all of the half- way houses. The State Police Liaison is also responsible for assisting and coordinating investigations with New Hampshire State Hospital Campus Security on an as-needed basis. The Liaison investigators work closely with personnel from the Department of Corrections investigating a wide variety of crimes including suspicious deaths, escapes, assaults, witness tampering, drug possessions, weapons possession and introduction of contraband cases occurring within the walls of the state correctional facilities.

During 2007, the Major Crime Unit conducted 75 investigations to include homicides, death investigations, suicide, police involved shootings, assault, sexual assault, and arson.