A direct numerical simulation of turbulent channel flow at $R{e}_{\tau }\approx 16000$ has been performed, providing the first channel-flow DNS in a Reynolds-number regime where inertial-layer behavior can be examined directly. Theoretical predictions associated with the inertial layer are assessed through the corresponding wall-normal derivative forms, allowing the wall-normal locations at which these asymptotic behaviors emerge to be identified quantitatively. The wall-normal Reynolds normal stress exhibits the clearest agreement with theory, allowing a candidate inertial-layer region to be identified directly. The dissipation-rate scaling is independently found to be consistent with the same wall-normal interval. These results provide direct evidence that inertial-layer behavior becomes observable at $R{e}_{\tau }\approx 16000$. The mean velocity exhibits two logarithmic-region candidates: one near the Reynolds-stress peak and another near the upper edge of the inner layer. The Reynolds normal stresses and dissipation rate also exhibit trends broadly consistent with their corresponding asymptotic predictions. However, the wall-normal locations at which these predictions are realized differ among the turbulence quantities. The present results suggest that inertial-layer behavior emerges progressively with increasing Reynolds number and that the degree of realization remains quantity dependent.