Take the following as truth: The prisoner had been arrested in consequence of the discovery, in his room, by Detective Inspector Japp ”a most brilliant officer ”of the identical phial of strychnine which had been sold at the village chemist's to the supposed Mr. Inglethorp on the day before the murder. 
Then the following statement: "The strychnine was used to assassinate the Duke." is true, false, or inconclusive?