If the original Perry Mason TV show was a 10, at best these movies are a 6. I gave this a 4 because Drake does even more stupid stuff than usual. I have to think that in order to get "Della" to sign on to do these movies she required them to hire her son to play the Paul Drake character. Aside from hair color he is completely wrong for the part.... One of the worst instances of miss-casting ever. William Katt just does not have the gravitas to play the Experienced Detective and on top of that the writers continually have him doing the stupidest of things which either tip off his hand or put him in situations where it's him against multiple people where he walks in begging to be cut off at the knees. In this movie he repeatedly creates situations in which his quarry gets away. In the woods, in the store, at the motel, on the highway he stupidly goes in with little or no planning and no backup, lets himself be seen and the quarry rabbits away. Infuriatingly stupid.
As to the movie itself, if the stupidity was removed I'd give it a 6 because it's a slightly different approach to a murder and because unlike the first 4 movies in the series it seems Burr had been feeling better (or the directors were more insistent he be a little bit animated) and was able to bring some semblance of life to his part. In the first 4 movies he was figuratively phoning it in.