CBI (Central Bureau of Investigation) is India's premier investigating agency, responsible for probing high-profile criminal cases, corruption scandals, and complex investigations. Established in 1942 as the Special Police Establishment to investigate corruption in government offices, it was later renamed the Central Bureau of Investigation in 1963. The CBI operates under the jurisdiction of the Department of Personnel and Training of the Indian government and has become the go-to agency for investigating cases of national importance, such as economic crimes, high-level corruption, and significant criminal activities.

The CBI handles cases involving serious criminal offenses, including financial fraud, murder, terrorism, and other organized crimes. It has jurisdiction across the country, and its involvement in a case often signals the gravity or complexity of the matter. The agency is also known for conducting high-profile investigations into political scandals and has been involved in cases such as the 2G spectrum case, the Coal allocation scam, and the Sushant Singh Rajput death case.

The CBI has often been praised for its competence and thoroughness in investigations but has also faced criticism for alleged political influence and delays in handling cases. It is often called the "last resort" when local police investigations fail or are suspected of bias.

In August 2024, BOOM investigated a viral letter claiming political interference in the Kolkata doctor rape-murder case. The Central Bureau of Investigation (CBI) confirmed through its official X handle that the letter was fake and clarified that no officer by the name mentioned in the letter exists within the agency, debunking the false claim.