OK, you are hiring a techie. How do you screen him / her? In order to effectively do that, you need to know the difference between knowledge and skill. The fact that you know something is knowledge. The ability do something is a skill. Now-a-days with the enhancements with search engine & public forums, it only takes few minutes to search for something. With this in mind, now ask yourself if you are looking for knowledge or skills. If you are looking for a short term contract, then yes, you don’t have much time for training and you would want the candidate to have both knowledge and skills.
It is easy to measure the level of knowledge, but how will you measure skills. Scenario based questions or a practical test would do the job. Also note that it is common for the candidate to be tensed at the interview and might not be in full capacity. Note that if you delay heavily and conduct many interviews, you might give up and begin to lower your standards. All the best. Feel free to share your thoughts