The case can be reviewed. The verdict cannot be amended, as the Attorney General herself said.

Obviously if there is new evidence, a new trial can take place. That is not what is being talked about in the petition on change.org, which is demanding a retrial because the signatories think the verdict is wrong. It is not based on new evidence.

Given that the defendants admitted their action but the jury decided it did not constitute criminal damage, it is hard to see what such evidence could be.