An autoinjector comprising: a case adapted to hold a medicament container having a needle; a needle shroud telescopically coupled to the case and movable between a first extended position relative to the case in which the needle is covered and a retracted position relative to the case in which the needle is exposed, a shroud spring biasing the needle shroud in a distal direction relative to the case; and a plunger rotationally and slidably disposed in the case, the plunger rotatable relative to the case between a first rotational position in which the plunger is engaged to the case and a second rotational position in which the plunger disengages the case, wherein the needle shroud engages the plunger to rotate the plunger from the first rotational position to the second rotational position when the needle shroud translates from the first extended position to the retracted position, the auto-injector further comprising: a cap removably coupled to the case, characterized in that the cap includes at least one compliant case beam (11.6) adapted to releasably engage at least one aperture (2.16) in the case, wherein, when the cap is moved in the distal direction relative to the case, the at least one compliant beam (11.6) disengages the at least one aperture (2.16) in the case and no longer radially abuts the case, wherein a force required to disengage the at least one compliant case beam (11.6) from the respective aperture (2.16) is greater than a force exerted by the shroud spring when the compliant case beam (11.6) is engaged in the aperture (2.16), further comprising a first shroud lock mechanism comprising one or more compliant beams (11.3) on the cap and a respective number of apertures (7.6) in the needle shroud adapted to receive each of the compliant beams (11.3), wherein, when the cap is attached to the autoinjector, the compliant beams (11.3) abut a radial stop (2.15) on the case which prevents the compliant beams (11.3) from disengaging the apertures (7.6). a case adapted to hold a medicament container having a needle; a needle shroud telescopically coupled to the case and movable between a first extended position relative to the case in which the needle is covered and a retracted position relative to the case in which the needle is exposed, a shroud spring biasing the needle shroud in a distal direction relative to the case; and a plunger rotationally and slidably disposed in the case, the plunger rotatable relative to the case between a first rotational position in which the plunger is engaged to the case and a second rotational position in which the plunger disengages the case, wherein the needle shroud engages the plunger to rotate the plunger from the first rotational position to the second rotational position when the needle shroud translates from the first extended position to the retracted position, the auto-injector further comprising: a cap removably coupled to the case, characterized in that the cap includes at least one compliant case beam (11.6) adapted to releasably engage at least one aperture (2.16) in the case, wherein, when the cap is moved in the distal direction relative to the case, the at least one compliant beam (11.6) disengages the at least one aperture (2.16) in the case and no longer radially abuts the case, wherein a force required to disengage the at least one compliant case beam (11.6) from the respective aperture (2.16) is greater than a force exerted by the shroud spring when the compliant case beam (11.6) is engaged in the aperture (2.16), further comprising a first shroud lock mechanism comprising one or more compliant beams (11.3) on the cap and a respective number of apertures (7.6) in the needle shroud adapted to receive each of the compliant beams (11.3), wherein, when the cap is attached to the autoinjector, the compliant beams (11.3) abut a radial stop (2.15) on the case which prevents the compliant beams (11.3) from disengaging the apertures (7.6).