If the seccies are being very aggressive in enforcing your execution, but are bad at searching you, or even removing your items at all, ask to be executed with lethal injection.
The moment the poison temporarily crits you, they'll see you as dead and put you in a bodybag, then typically leave it to the brig phys to process.
The crit will be over for a few moments, in which you can inject yourself with charcoal and grab a oxygen pill (forgot the name) before the crit strikes again.
Remember to close the bodybag again, the brig phys will most likely morgue you, if the coroner is just as watchful, you've might just successfully escaped death.
Speaking from personal experience, I died in my case, but was cloned and investigated my corpse.
That round went on to three different deaths, all providing interesting data for me in the future.