Description:  An individual employee may be the custodian of ESI located on his/her local computer(s), hard drives, media as well as specific network storage locations under their sole administrative control. Even though a member of the IT department is usually the administrator of email and other systems, the ESI from some of these systems is still associated with the individual custodian. For example the user's mailbox, phone messages and more. the volume and types of ESI associated with a custodian will vary by department and position.

Metric: By total size or items. Size will usually be in GB, while item counts will require explosion of container files (PST, ZIP, TAR). The total time per custodian may include that time to generate retention notices, to make retention copies and all other actions associated with preservation of that custodian’s individual ESI. Where efforts and volume overlap with other ESI systems and sources, you should prioritize and allocate to the highest priority source.