Such a discovery would basically contradict the Fundamentalist Christian view of the Bible and would create a ruckus among them not just the JWs.
The first discovery of potential life will not be able to directly detect life but only the unique atmosphere it grows in. If it's similar to Earth with a substantial Nitrogen/Oxygen atmosphere then that will be an indication that there's something alive on that planet. Otherwise the atmosphere in a non-living planet would be mostly Carbon Dioxide.
This would be detected by analyzing the light between the planets' star - its sun - as it goes through the planets atmosphere. Our telescopes are not quite able to do this for Earth like planets at the present moment but better technology preferably a space built giant telescope would be.