Asn to forensic nursing certificate or bsn to masters in forensic nursing

Hello
i have the asn and continuing for the bachelors in nursing. My question is can i do my bsn and do the forensic nursing certification, or do i have to do the forensic nursing cert. And masters? Or the masters only? It all depends on the employer, which one is better to have based on job related? And what else i need to become a forensic nurse?