To enable searching for records using criteria in associated cases, enable the ‘Case Search’ section from ‘Administration’ / ‘Customize Pages’ / ‘Search Page Customization’.

Customize Pages - Provides The Ability to Enable / Disable & Change Labels

Case Search Available Fields
Click the checkbox in the upper right hand corner to turn this section on and then click on the fields you want to enable.
The ‘Search Records’ page displays searchable case criteria.

Case Search Available Fields
Click the checkbox in the upper right hand corner to turn this section on and then click on the fields you want to enable.