At about the half way point when Sandra Keller goes running after Hardtack, what she is wearing changes color, going from light to dark and back to light again. The actress Natalie Trundy apparently wore something warmer when she was outdoors on location than when she was on the sound stage (this scene likely was filmed sometime in the middle of winter).
In a conversation with the banker, Mr. Osgood, Mrs. Doyle refers to the deal with "old Mr. Keller, or rather, his daughter" -- the deal was actually with Mr. Keller's granddaughter.
After providing testimony on the decedent's cause of death, the autopsy surgeon went on to testify regarding the cause of a tear in the decedent's trousers. In real life, the judge would have stricken this, as it falls outside a medical expert's purview; the testimony would had to have come from an expert witness on criminal investigations (like Lt. Anderson, who was the prosecution's next witness).
Mentions the War Department being contacted to confirm the Medal of Honor. The War Department was dissolved in 1947 and replaced by the Department of Defense in 1949.
When Lt. Anderson discovers the hidden shotgun, he picks it up in both hands, clearly gripping the most obvious locations that would have fingerprints, something an actual police detective would be highly unlikely to do. This happens in Perry's presence, but Perry never questions the fingerprint findings in any way. But Anderson picked the shotgun up by the wooden stock, which was at the time unlikely to hold viable fingerprints. When testifying, he said they found "on the metal parts of the gun, several fingerprints..." He never touched any of the metal parts when he picked it up at the Keller house.
During his cross-examination of Amos Keller (Arthur Hunnicutt) DA Hamilton Burger mentions that he had contacted the War Department concerning Keller's award of the Medal of Honor. The War Department had been replaced by the Department of the Army with the National Security Act of 1947. Since this episode was filmed during 1962-1963, this was some 15 years after the War Department had been abolished.