You can run an advanced query to search for Project Tracker artifacts by defining a user as the search criterion.
Once you have selected all the personnel you require, click Add Assignee and click Done.
Using the Search for artifacts with no associations section you can define a search for artifacts for which no assignees with a particular user attribute have been associated. For instance, if you have a "QA Lead" user attribute defined for your project and want to know which issues have not been assigned a QA Lead, you can elect to search for all artifacts with no association of type "QA Lead". You can choose as many user attributes as you need for your query.