I. Theory
Modal verbs are often used in conjunction with other infinitives to convey ability, volition, or necessity. Examples in English include:
can, want, and
must. Although these verbs have both
Perfekt (haben gekonnt) and
Präteritum (konnten) forms, each is found in specific contexts.
II. Modal Verbs in Perfekt (present perfect)
German modal verbs are found in the present perfect only when they do not accompany an infinitive. This is rare as most of the time, an infinitive is necessary. However, infinitives are sometimes inferred by context. The modal past participles are:
gedurft, 