on (someone's) (own) head be it

slightly formal

something that you say in order to tell someone what they intend to do is silly and they must accept the blame or responsibility if it goes wrong.

If you don't want to take out any insurance, ok, but on your head be it.

• down on something
• down on your luck
• down the drain
• Down the hatch!
• down the line
• down the pike
• down the road
• down the toilet
• down the tube
• down the tubes
• down-to-earth
• down tools
• down to the wire
• Down Under
• do you have the time
• do you know something
• Do you mind!
• do you mind
• do your best
• do your bidding
• do your bit
• mind your own business
• Mind your own business!
• mind your p's and q's
• Mind your step.