The first step in ensuring preservation of relevant data under a legal hold is to suspend any automatic data deletion or archiving that may affect the involved data sets. This is critical because if the data continues to be altered or deleted following a legal hold notice, it could result in spoliation of evidence, which can lead to legal penalties. Initializing backups is a good practice for preserving evidence, but it is not the first step since it does not prevent ongoing data loss. Encrypting data maintains confidentiality but does not prevent data alteration or deletion. Shutting down systems may preserve data but is not usually the first step and can disrupt business operations.