Search two Crimes/Thriller from the 50s/60s years, acquitted, citation

Hello to all you  Reader, a fabulously suspenseful rare unknown Thriller (French/British?) in which a man pushes his wife down a ravine while she is taking pictures with her camera.Even as she falls, she turns andtakes photos of the murderer, of her husband.Of course he immediately climbs down into the gorge, but cannot find the camera. The inspector later identifies the perpetrato through the photos.I was already thinking of "Le meurtrier" (The Blunderer),by Patricia highsmith,unfortunatelyit wasn't that one.2) Probably a us production, fordiscerning crime film lovers, wanted film is under the motto: "Two lies that make one truth"The suicide note from a long- dead woman reveals the following:her daughter had been murdered by her husband (i.e., the writer's son-in-law); but he was acquitted. When the mother fell ill (and probably saw her end near),she poured poison into a water bottle, wiped her fingerprints off and asked her son-in-law to serve her a glass of water. He was then sentenced to death, the discovery of the letter came too late for him.Closing words (voice of the older woman): "Two lies that make up one truth."I am very grateful for reading any kind of help.greeting Maximilian