I'm going to go home and watch this now, and I'll post in the comments to let you know how I like it. I haven't seen it in (Jesus Christ!) forty years, but I loved it when I was 15. James William Guercio is better known as a record producer (Chicago, Blood Sweat and Tears), and this was the only film he ever directed-- but in 1973, it was the American entry at the Cannes festival (So I guess every country submits a film? I'll admit that I know nothing about how this works), and it was a big hit there according to the advertising blurbs in the New York Times. I remember tightly controlled cinematography, a lot of close-ups of things. I was impressed by such things back then.
Robert Blake (Before Baretta) plays a motorcycle cop, and he solves a murder. I don't remember much more, but the trailer looks great.