TSH simulations of thymine photodynamics have been reported using MRSF-TDDFT, which support trapping on S 1 as the explanation for a long-lived (∼ 5 ps) decay component time-resolved experiments. This is consistent with multireference results that include dynamical electron correlation, but it is at odds with CASSCF predictions that indicate trapping on S 2 . The discrepancy appears to originate in an excited-state barrier that is too high in the absence of dynamical electron correlation, supporting other results indicating that CASSCF is not a quantitative method for excited-state dynamics.