Birbal Trilogy Case 1: Finding Vajramuni or simply known as Birbal^[2] is a 2019 Indian Kannada-language crime thriller film written and directed by M. G. Srinivas.^[3] The film is the first installment of the Birbal Trilogy. It also marked the third character-based trilogy in Kannada cinema, after CID 999 and Sangliyana.^[4] It is also the first installment in a cinematic universe followed by Ghost in which M. G. Srinivas reprises his role.

Rukmini Vasanth made her debut as a lead actress.^[5] The film introduced an 8D song for the first time in Kannada cinema; it was also the first Kannada film to use the Scribble effect.^[4][6][7] Its sequels are titled Birbal Trilogy Case 2: Avrn bitt, Ivrn bitt, Ivryaru? and Birbal Trilogy Case 3: Turremane.

The movie was praised for employing the Rashomon Effect in its story narration technique.^[8] The movie is based on the 2017 Korean movie New Trial.^[9] The Telugu remake of the film Thimmarusu released on 30 July 2021.^[10][11] The movie was also reported to be remade in Tamil.^[12][13]

In Bangalore, Mahesh, an intelligent lawyer working for Hegde, a law firm head, is assigned to investigate the case of Vishnu, who is suspected of killing Ramdas, a taxi driver and a police informer 8 years ago. Mahesh learns that Vishnu is released from prison, where he along with his girlfriend Jahnvi and Shastry visit him at his village. Vishnu says that he was returning from work that night and gets injured in an accident, where he found Ramdas lying dead in the taxi and called the police, but the cops led by Inspector Raghavan, forces Vishnu to take blame for Ramdas' death after finding a knife in his scooter.

Mahesh begins his investigation, where he learns that the bar owner (where Vishnu is actually working) had tried to molest his friend Sheela, but Vishnu saved her and sent her away from the city. Through Sheela, Mahesh and Vishnu learn about an article describing the murder which was published 9 months ago, after Vishnu's imprisonment. They meet a retired police officer and learn that Suri, a call center employee, was behind Ramdas's death. Mahesh, Vishnu and Shastry capture Suri, who reveals that Raghavan used to make Suri and other young men commit robberies. Suri tried to force Ramdas to give money, but he accidentally stabbed Ramdas and escaped.

Fearing that his illegal activity would be exposed, Raghavan framed Vishnu and had him imprisoned, where he also makes Suri to pretend that he is mentally unstable. Vishnu tells Mahesh to present Suri in the court, but Mahesh refuses as the court already declared Suri as a mentally ill person and begins to find more clues. Later, Mahesh learns that the truck driver was at the murder spot, where he learns from a truck driver that a boy named Amoghavarsha took a lift in order to escape as he witnessed Ramdas' death. Mahesh finds Amoghavarsha and learns that he was returning home from a bar where he witnessed Ramdas' death and recorded it in his camera.

Later, Raghavan arrests Amoghavarsha for harassing the girl, which leads Mahesh to discover that Jahnavi was bribed by Raghavan to spy on Mahesh during his investigation. In the court, Mahesh manages to prove Vishnu's innocence and Raghavan is suspended. Later, Mahesh finds from the video that another person was present and behind Ramdas' death, where he traces the killer's bike and learns that the bike owner Narayanappa is a constable, who died from a stroke. Meanwhile, Raghavan kidnaps a person where Vishnu witness this and tries to kill Raghavan, but Mahesh stops him and Raghavan is arrested.

Mahesh takes a number from which Narayanappa received blackmail calls, where he devises a plan and manages to identify the killer, who is revealed to be a retired inspector named Vajramuni. Mahesh reveals himself as Ramdas's son and also knows that Vishnu was not present at the time of his father's death. With Shastry's help, Mahesh joined Hegde's law firm and secretly opened Vishnu's case. Mahesh had learnt about a memory card which revealed that Vajramuni had committed gruesome murders of various business persons' rival in the form of police encounters, where Ramdas learns about this from a grave caretaker. Fearing that he would be exposed, Vajramuni told Narayanappa to silence Ramdas. After the conclusion, Vajramuni gets arrested and sentenced to prison.

• M. G. Srinivas as Mahesh Das, a lawyer
• Rukmini Vasanth as Jahnvi, Mahesh's girlfriend
• Madhusudhan Rao as Inspector Raghavan
• Sujay Shastry as Shastry
• Vineeth Kumar as Vishnu
• Suresh Heblikar as Hegde, a law firm head
• Ravi Bhat as Ramdas
• Aruna Balraj as Sumitra, Vishnu mother
• Keerthi Baanu as Retired Inspector Vajramuni
• Krishna Hebbale as Parthasarathy, a public prosecutor
• Kavitha Gowda as Sheela (cameo appearance)
• Sandeep Jain as Suri (one of the Antagonist)

The soundtrack and background score were composed by Saurabh Vaibhav and Kalacharan. It was released under the label of Crystal Music.

The director's efforts, an engaging screenplay, the cast's performance and the background score received praise from the Bangalore Mirror, but was critiqued as having a slow-pace, being overwritten and being too long.^[14] It was reported that Hindi film makers had approached the director and producer for the remake rights.^[15] The movie released on online platform Amazon Prime on 20 April 2020.^[16]