Oru CBI Diary Kurippu is a 1988 Malayalam mystery film directed by K. Madhu, written by S. N. Swamy, and starring Mammootty, Suresh Gopi, Jagathy Sreekumar, Mukesh, and Sukumaran. This film is the first in the series of the CBI investigative thrillers featuring Mammootty as CBI officer Sethurama Iyer. It was produced by M. Mani under the banner Sunitha Productions. Sequels to the film are Jagratha, Sethurama Iyer CBI, and Nerariyan CBI. A fifth sequel Veendum CBI in the franchise has been announced and is now in the pre-production stage. The plot-line of the film, Oru CBI Diary Kurippu, was crafted around a real life incidence, the Polakkulam Case in which a hotel employee was murdered and dropped from the terrace to make it look like a suicide. The case was investigated by the CBI and it was in this case that a humanoid dummy experiment was first done in the state of Kerala to prove a murder case. The lead character, Sethurama Iyer is inspired by a police officer named Radha Vinod Raju, Jammu and Kashmir cadre IPS Officer who in 2009 was appointed as the first chief of India's National Investigation Agency.