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:  The metrics associated with an individual custodian include the estimated total volume of ESI and the time and resources required to identify both the identity of the custodian and the volume of potentially relevant ESI, It is the process of identifying custodians that is being measured here.  The metric is the time and resources required to identify the various Custodians and to assess the potentially relevant ESI that each may possess.