An original study combining spin polarization with hot-electron transport in a 3-terminal double tunnel junction device is presented. We report for the first time a tunnel magnetoresistance signal for each tunnel barrier in an integrated device made with two different insulating materials. Furthermore, a hot-electron transfer from the emitter to the collector, both magnetic, through the base and both tunnel barriers is presented with an appropriate set of applied voltages. The characteristics of the hot electrons have been successfully modeled theoretically on the basis of experimental tunnel barrier parameters. However, in contrast to the theory, no field dependence of the hot-electron characteristics was measured. Possible origins for this discrepancy are discussed.