Can we tell when people are lying
There is a huge industry around detecting lies. For instance, many insurance companies use voice stress analysis in an effort to spot bogus claims. The reality though is that despite much research and grand claims, technology has not yet proven effective.
The polygraph lie detector was developed in the early Twentieth Century and measures various physiological parameters such as skin conductance, pulse, blood pressure and respiratory rate. The theory is that lying is stressful and the stress response will be shown in changes in physical signs. There are various problems with this--not least is that the subject is likely to be answering 'stressful' questions lying or not. Also it is fairly easy to fake by biting your tongue, pinching yourself or clenching your anal sphincter!
The interpretation of the results is highly subjective with different 'experts' giving different opinions. Overall studies show the polygraph is only slightly better than chance. Generally speaking polygraph results are not admissible in courts due to these problems.
Other strategies using monitoring eye movements, pupil size and also brain activation via fMRI. Although fMRI has shown positive results these have only been in highly controlled situations and the efficacy rapidly breaks down as the scenarios become more 'real world'.
See here for a more detailed overview from Psychology Today
If you want to abandon technology and rely on your own senses then again you are much worse than you think. People in jobs were they have supposed skill in this area, such as police, are just as bad as everyone else but may rate themselves even higher.
Skeptoid a critical thinking site, run by Brian Dunning, which does some great blogs and podcasts has an episode about this which is well worth a listen.