In one scene a woman who has been blacklisted commits suicide by backing her car over a cliff. The car is clearly a Chevrolet of 1942-1947 vintage and no later. We have a glimpse of the automatic transmission indicator being moved from Park to Reverse, then the car lurches backward and over the cliff it goes. But Chevrolets of that vintage did not have automatic transmissions. "Powerglide", (the first Chevy automatic transmission) was introduced in 1950.
When the De Niro character visits Zanuck watching dailies early on in the movie, we see that the dailies on screen are Marilyn singing a number from "Gentlemen Prefer Blonds" and Zanuck tells "Howard" (Hawks) the director (on the phone) that he can't see any difference in the various takes. "Gentlemen Prefer Blondes" was filmed and released in 1953, but the last scenes of "Guilty By Suspicion" are Feb 1952.
Before going to London, Joe is seen editing the classic The Boy with the Green Hair, but the movie was already released in 1948 and Guilty by Suspicion story takes place in the 1950's.
Ms. Nolan's car, a 1941 Chevrolet, is supposed equipped with Powerglide automatic transmission. Powerglide was not offered on Chevrolets until 1950.
When Robert De Niro meets with Sam Wanamaker and Tom Sizemore in the flophouse hotel, Wanamaker pours himself a shot of Maker's Mark Bourbon. The movie is set in 1951. Maker's Mark didn't exist as a brand until 1958.
There is a Milwaukee Braves baseball pennant on the wall of Merrill's son's room. This film takes place in 1951 and 1952. The Braves didn't move to Milwaukee from Boston until 1953.