A man accused of murdering his missing American girlfriend was not guilty because she could still be alive and continuing her “below the radar” lifestyle, a jury has heard.

The complaint brought by a 12-year-old transgender child will proceed as a class action-style case, meaning hundreds of children can lodge a claim.

Ashley Paul Griffith had argued the 27‑year non‑parole period for hundreds of sexual offences against children was manifestly excessive.