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 ​