An argument from first principles is presented in favour of native-speaker involvement in Language Analysis for the Determination of Origin (LADO). Speech is both language and action, and too little account has been taken in debates over LADO of the fact that the physical act of speaking involves coordinating a mechanism (the vocal organs) with myriad degrees of freedom. Part of what a native speaker has acquired will consist in imitated motor behaviour too detailed for description by phonetic categories. Examples are cited where sounds differing in dynamics, coordination and alignment are given the same linguistic phonetic analysis. Throughout history, making the judgment ‘(not) one of us’ from speech has been a central social skill. The default assumption (until disproven) must be that native-speaker knowledge of the dynamics of speech as action must add delicacy of discrimination to that achievable using linguistic descriptions.