David Harriman (plaintiff) was arrested and brought to jail in October 2006. Harriman was extremely intoxicated at the time. A few hours after arriving at the jail, Harriman was transported to the hospital. What happened to him in the interim was disputed. According to correctional officers, Harriman was raving in his cell just after 10 p.m. when he fell and hit his head. Officers entered the cell and saw Harriman in a puddle of his own urine. Harriman then had two seizures. Around 10:20, an ambulance was called. When it arrived, an EMT named Jenny Sheriff attended to Harriman. Harriman’s recollections from the night were few: he recalled “hollering”; “flashes of light”; seeing his wife’s cousin, Foster Kane, who was also being held at the jail; and the smell of “urine mixed with cleaning fluid.” Contending that officers had beaten him in jail, leaving him with a long-term brain injury, Harriman sued Hancock County, the sheriff, and several correctional officers (collectively, defendants) in a federal district court in April 2008. A magistrate judge set scheduling dates: initial disclosures were due July 30, 2008; discovery was to close December 3, 2008; dispositive motions were due January 15, 2009. Defendants filed a motion for summary judgment on its due date. On February 17, 2009, two days before Harriman’s response to the motion was due, his attorney submitted a “supplemental” initial disclosure identifying Kane and Sheriff as additional persons likely to have discoverable information. This was not the first time that Harriman had missed a deadline. Here, he claimed that Kane and Sheriff were only recently located, through a private investigator hired on January 9, 2009. Harriman responded to defendants’ summary judgment motion, relying on affidavits of Kane and Sheriff that sharply contrasted with defendants’ version of events. Defendants moved to strike the affidavits. The magistrate ruled in their favor, precluding Harriman from using the affidavits and recommending that summary judgment be granted to defendants. The district court adopted the magistrate’s recommendations and granted summary judgment. Harriman appealed.