The supervisors of the thesis, together with the doctoral student, can prepare an initial proposal of members of the tribunal which will evaluate the defence of the thesis.
As in the case of external evaluators, the initial proposal must be approved by the Academic Committee, which will in turn make the formal proposal to the UPV Doctoral School. This proposal may be made in parallel to the proposal of external evaluators.
In this link you will find more detailed information about this action.