One victim is crushed to death in a printing press, resulting in text being printed neatly all over his face and body. However, as the press closed it would not be able to print text cleanly and exactly around the curvature of his head and body. Instead, the body would show signs of extensive crush injuries and the printed text would be distorted round the curves.
Nelson would not be picking up books at a crime scene without gloves.
The printing press platen of font lifted off the murder victim did not have any ink on it.
As Barnaby and Nelson are driving away from the illicit poker game the car starts moving while the sound of the engine starting can still be heard.