How to judge technical skills of developer

To judge a technical ability of programmer ask about his past technical work, ask some general tech questions and If you can, try to give him/her a little challenge where he/she can prove some of the skills he/she have enumerated on his/her CV and that he/she will need for the job. In a further interview you may ask him/her how he/she solved some problems. If it is the case, ask him/her how he/she did certain aspects of items listed in his/her portfolio.

Assessing technical aptitude has to be some what planned to be in adavnce. Since the interview is preplanned, it is good to prepare some techie questions and answers before conducting the interview. Nowadays a lot of techie materials, interview questions, answers are available in the internet. Having a technical expert in the interview panel is also a good idea.