<p>In one aspect, a method for determining a validity of an identity asserted by a speaker using a voice print that models speech of a user whose identity the speaker is asserting is provided. The method comprises performing a first verification stage comprising obtaining a first voice signal from the speaker; and comparing it with the voice print. The method further comprises performing a second verification stage if it is concluded in the first verification stage that the first voice signal was obtained from an utterance by the user, comprising adapting at least one parameter of the voice print, obtaining a second voice signal from the speaker, and comparing it with the adapted voice print to conclude that the second voice signal was obtained from an utterance by the user.</p>
