The level of detail you are seeking would be practically impossible to find for any matter of "expert". Even if you were provided a list of their projects and

The level of detail you are seeking would be practically impossible to find for any matter of "expert". Even if you were provided a list of their projects and their involvement, how would you know their competence without reading code and understanding implementation details? Further still, can you even trust yourself to provide a competent assessment of their designs and implementation? A single security breach should not invalidate ones credentials more than a single lost patient should invalidate a Dr's medical license, with the exception being cases of gross negligence or malfeasance.