To design a GUI that supports collaboration among legal teams, consider the following:

1. Multi-user access: Allow multiple users to access and edit documents simultaneously.

2. Real-time commenting: Enable team members to leave comments and feedback in real-time.

3. Task assignment: Allow users to assign tasks and track progress.

4. Document versioning: Track changes and revisions to documents.

5. Secure sharing: Enable secure sharing of documents with external parties.

6. Centralized repository: Store all case-related documents in a centralized location.

7. Search and filtering: Provide robust search and filtering capabilities.

8. User roles and permissions: Define user roles and permissions to control access.

9. Notification system: Send notifications for updates, changes, and deadlines.

10. Integration with communication tools: Integrate with email, chat, and video conferencing tools.

11. Customizable workflows: Allow teams to create custom workflows and templates.

12. Mobile accessibility: Ensure the GUI is accessible on various devices.

13. User-friendly interface: Design an intuitive and user-friendly interface.

14. Training and support: Offer training and support resources.

15. Security and compliance: Ensure the GUI meets legal industry security and compliance standards.

By incorporating these features, you can create a GUI that facilitates effective collaboration among legal teams, enhancing productivity and case outcomes.