The interplay of electronic correlations, multi-orbital excitations, and spin-orbit coupling is afertile ground for new states of matter in quantum materials. Here, we report on a polarizedRaman scattering study of semimetallic SrIrO3. The momentum-space selectivity of Ramanscattering allows to circumvent the challenge to resolve the dynamics of charges with verydifferent mobilities. The Raman responses of both holes and electrons display an electroniccontinuum extending far beyond the energies allowed in a regular Fermi liquid. Analyzing thisresponse within a memory function formalism, we extract their frequency dependent scat-tering rate and mass enhancement, from which we determine their DC-mobilities andelectrical resistivities that agree well with transport measurement. We demonstrate that itscharge dynamics is well described by a marginal Fermi liquid phenomenology, with a scat-tering rate close to the Planckian limit. This demonstrates the potential of this approach toinvestigate the charge dynamics in multi-band systems.