The assumption that the photodissociation of HI proceeds adiabatically is re‐examined in the context of recently calculated alignment parameters, a(⟂), for the ground state halogen atoms resulting from photodissociation of the analogous HCl and HBr molecules. The a(⟂) alignment parameters for HCl, HBr, and HI are determined from time‐dependent quantum mechanical wave packet calculations based on the best available ab initio electronic structure for each molecule. The experimental measurement of the alignment of the I(²P_3/2) atoms is proposed as a stringent test of whether the photodissociation is adiabatic or involves non‐adiabatic coupling of the A¹Π₁ and a³Π₁electronic states.