Which effect takes precedence? As the defender, can I change the hit to a focus before the Mercenary co-pilot changes the hit to a critical?

Attack dice: Defender changes first, then attacker.

Defense dice: Attacker changes first, then defender.

So yes, Sensor Jammer goes first. But if the attacker has a focus they can spend the focus to change that eyeball (along with the others) to a hit, and then use the Mercenary Copilot to change it to a crit.

The rules specify that the defender would modify all attack dice before the attacker does. So yes, Sensor Jammer would make the *hit* a *focus* before the Mercenary Copilot can make it a *crit*.

But may inadvertently set them up if you have Marksmanship active or a focus token handy or something.