The film begins with a drunk Rahul Dewan racing in a Toyota Land Cruiser Prado against an Audi, after he is seduced by a woman in the passenger seat. He loses control and crashes into a wall on the footpath by the road. The film cuts to a court scene where Sakthivel, an LLB graduate defending a surgeon against a Public interest litigation (PIL) filed against him after the surgeon had his son operate upon a pregnant woman in his pursuit of Guinness Book of World Records. Sakthi loses the case but decides to move to the capital Chennai to try his luck. He happens to see prominent criminal lawyer Adhiseshan defending Rahul in a sessions court. Rahul is accused of causing death under the influence of alcohol. Adhiseshan convinces the judge that prosecution had no evidence to implicate Rahul and that he was being deliberately targeted by the media as he was from a rich family, resulting in Rahul's acquittal.
Adhiseshan, though, is not satisfied with the fee paid by the Dewans. Sakthi, desperate to have some money and fame, decides to pursue the case and files a PIL in the court against Rahul Dewan's acquittal. After initially reprimanding Sakthi for his mistakes in filing the PIL and taking the press reports as an evidence, Justice Dhanapal gives a date for hearing and warns Sakthi to collect some evidence before the hearing. He then runs into Vijay Nair, who claims to have witnessed the accident. Then Sakthi introduces him as a witness in the court and Dhanapal, after cross-examining him, gives a date for the next hearing. He also summons Rahul to be present in the court for the hearing.
Sakthi becomes a celebrity overnight and is admired by Moorthy, who donates a room in his restaurant to Sakthi for using it as his office. However, Sakthi's plans turn upside down when Vijay reveals to him that he is no witness, but a crony of Adhiseshan and it was part of a plan to extract more money from the Dewan clan. As part of the deal, Nair gives Sakthi his share of the money paid by the Dewans to silence Nair. Sakthi gleefully accepts the money and regrets that had he known this plan earlier, he would have demanded more money. Nair turns hostile in the court, and Sakthi accepts the statement given by Nair. Dhanapal postpones the judgement for the next hearing. Priya Dharmalingam, the cousin and fiancée of Sakthi, chides him for compromising on justice for his greed. Sakthi realises his mistake once. Moorthy slaps him for his treachery. He returns the money to Adhiseshan and challenges him to win the case.
With the help of his uncle Surya, Sakthi collects the video footage of the Land Cruiser involved in the accident and presents it to the court. Though Adhiseshan counters him that the Land Cruiser was driven by the driver of the Dewan family, Sakthi refutes his statement by submitting the necessary evidence. Dhanapal orders the Police to provide a bodyguard for Sakthi after he was seriously beaten up by alleged assistants of Adhiseshan. Sakthi and his friends try to interview a relative of one of the victims, Muthupandi, but he says that he knows nothing. Sakthi and Priya decide to leave, but as they get on the scooter, a lorry hits them, injuring Priya. At the hospital, Muthupandi tells Sakthi that a survivor of the accident stays in Vandavasi and Sakthi and one of his friends decides to leave for Vandavasi. Inspector Selvam tries to sabotage Sakthi's investigation but Sakthi is rescued by his bodyguard. Sakthi and journalist Jennifer arrive at Vandavasi, but the police, who captured Muthupandi, kidnap the survivor.
The next day, Sakthi reveals that he brought the survivor, thanks to Muthupandi intentionally showing the police the wrong man, and Sakthi prosecutes Selvam and finds that he has botched up the investigation by declaring Kamalakannan (Raja Rishi) as dead and snatching Kamalakannan's hard-earned money to stop him from killing Kannan. Kamalakannan testifies that he woke up that night to see his family lying in a pool of blood and Rahul getting out of the car, and after seeing what he has done, Rahul spotted Kamalakannan and ran him over with his car, so no there will be no witnesses. Kamalakannan survived, with his leg being broken. Dhanapal tells Rahul to come to the podium and orders Kannan to see if Rahul was the driver. Kannan confirms that Rahul was the one who drove the Land Cruiser. After a conclusion of arguments and counter-arguments between Adhiseshan and Sakthi, Dhanapal directs the Tamil Nadu Police to suspend Selvam and initiate a criminal inquiry against him and also declares Rahul as guilty of the crime and sentences him to 14 years in jail under Section 304 and under section 307 of the Indian Penal Code. While Sakthi celebrates with his team, Adhiseshan is crestfallen over suffering defeat for the first time.
Throughout 2014, director I. Ahmed and producer-actor Udhayanidhi Stalin planned a film titled Idhayam Murali, which would also feature Hansika Motwani and Ashok Selvan.[1] However, the team were unable to begin production and decided to stall the venture, instead choosing to remake Subhash Kapoor's 2013 Hindi film, Jolly LLB.[2] Unlike the original film, which was a comedy drama, Manithan was made to be more serious and dramatic.[3] Motwani was retained as the heroine of the project with Prakash Raj and Radha Ravi added to the cast, and Santhosh Narayanan signed as the film's imposer.[4] Production began in August 2015, with the film remaining untitled throughout production.[5]Vivek also joined the cast, while Aishwarya Rajesh was signed on to replace Akshara Gowda, after the makers had a change of heart about casting the actress.[6][7]
The film was revealed to be reaching completion by early December 2015, before the film's set was destroyed in Saligramam following the 2015 South India floods.[8][9] The title of the film, Manithan, was announced on 14 January 2016, coinciding with the release of the film's first poster.[10][11] The makers initially thought of titling the film Shakti, after the lead character, until Vivek suggested Manithan. To secure this title, the team obtained permission from AVM Productions, the producers of the 1987 film of the same name.[12]
The film's soundtrack album and background score were composed by Santhosh Narayanan. The soundtrack album consists of five tracks. The extra song Kaichal was not officially released, however was featured in the film.
Malini Mannath of The New Indian Express wrote, "The courtroom drama with its twists and turns, is engaging and well crafted. With its solid screenplay and its light-hearted take, Manithan is worth a watch".[13] Lata Srinivasan of DNA India wrote, "Manithan works because of the casting and the fact that one lawyer from nowhere decides to fight for justice for the have-nots. It’s a feel-good film that has you rooting for the weak and shows you that being a manithan (human) is important".[14]
