It’s a bad idea for real life, which is probably why it would make good fiction.
You don’t need both potential and future. If you don’t mean to imply that the people detected will murder, only that it’s likely, use potential.
The second sentence begins, Those who were tested positive as a potential murderer… At the least, this should be changed to, Those who test positive as potential murderers — if you’re talking about a plural subject, keep it plural.
Other changes were made for clarity and flow (including chopping out a part of the second sentence that I just told you how to fix).
A machine has been created to detect potential murderers. Those who test positive are sent to a deserted island to fend for themselves. You are one of those people.