The inhibitor DEVD-CHO does not seem to inhibit NucView™ 488 staining.
FAQ from Biotium
DEVD-CHO is a reversible inhibitor and may not sufficiently block caspase-3 activity. Adding an irreversible inhibitor like DEVD-FMK at the beginning of the experiment (before or at the time of apoptosis induction) may more effectively inhibit caspase activity.