When Mr. Blonde is torturing the cop he has him duct taped to a chair. His hands are tied, there is tape around his upper body, and around his ankles holding them to the legs of the chair. However when Mr. Blonde dumps the gasoline on the cop the cops legs kick up in the air as if they weren't taped down. Then in the next shot of the cop they are taped down again.

Just a side note: Something a lot of people miss is at the very end when Mr. Pink runs out of the warehouse. You can hear police sirens and if you have a good sound system you can distinctly hear Mr. Pink yelling "don't shoot I'm a cop."