In this story, the case of the murder seems to be open and shut. This means that it is really obvious that the accused is guilty and it will be easy to convict him.
There are two main reasons why this case is going to be so easy.
The first reason is that the accused man, Adams, looks very distinctive. He has bulging eyes and a very strange physical appearence. That means it will be hard to mistake someone else for him.
The second reason is that there are 4 witnesses who have all seen him quite clearly in very incriminating circumstances.