Scott based his legal argument on precedents such as Somersett v. Stewart, Winny v. Whitesides, and Rachel v. Walker, claiming his presence and residence in free territories required his emancipation. Scott's lawyers argued the same for Scott's wife, and further claimed that Eliza Scott's birth on a steamboat between a free state and a free territory had made her free upon birth.
It was expected that the Scotts would win their freedom with relative ease since Missouri courts had previously heard over ten other cases in which they had freed slaves who had been taken into free territory. Furthermore, the case had been assigned to Judge Alexander Hamilton, who was known to be sympathetic to slave freedom suits. However, in June 1847, Scott lost his case due to a technicality: Scott had not proven that he was actually enslaved by Irene Emerson. At the trial, grocer Samuel Russell had testified that he was leasing Scott from Irene Emerson, but on cross-examination he admitted that the leasing arrangements had actually been made by his wife Adeline. Thus, Russell's testimony was ruled hearsay and the jury returned a verdict for Emerson.