This work analyzes the performance of speaker recognition when carried out by human lay listeners. In forensics, judges and jurors usually manifest intuition that people is proficient to distinguish other people from their voices, and there fore opinions are easily elicited about speech evidence just by listening to it, or by means of panels of listeners. There is a danger, however, since little attention has been paid to scientifically measure the performance of human listeners, as well as to the strength with which they should elicit their opinions. In this work we perform such a rigorous analysis in the context of NIST Human-Aided Speaker Recognition 2010 (HASR). We have recruited a panel of listeners who have elicited opinions in the form of scores. Then, we have calibrated such scores using a development set, in order to generate calibrated likelihood ratios. Thus, the discriminating power and the strength with which human lay listeners should express their opinions about the speech evidence can be assessed, giving a measure of the amount of information given by human listeners to the speaker recognition process.