The judges are looking for somebody who can shine in content, clarity and charisma.
The content of the presentation must be scientifically accurate. If the topic chosen has controversy or uncertainty around it, then the talk must acknowledge the opposing views. The scientific topic presented should be well chosen to suit the audience.
Clarity is critical for effective science communication. The structure of the presentation must enable the audience and judges to easily follow the talk and they should be left with a full understanding of the scientific concept chosen.
The audience and judges should be left inspired and enthused about science. The winner will be a charismatic presenter who makes the science easy to listen to, entertaining and exciting. He/she should not only be able to communicate the science but share their passion for it and leave the audience wanting to learn more.