A needle assembly adapted for fluid communication with a cartridge containing a substance to be delivered to a subject, the needle assembly characterized by a biasing device (70) arranged to apply a biasing force on a needle (28, 116) to cause the needle (28, 116) to protrude outwards of a housing (30, 112) to pierce the subject, and biasing device release apparatus (60) including a biasing device arrestor (62) that initially blocks movement of the biasing device (70) and which releases the biasing device (70) when the safety latch (32, 122) moves to a position that permits moving the needle holder (26, 118) to cause the needle (28, 116) to protrude outwards of the housing (30, 112).
