How Do You Evaluate A Software Engineer Or IT Professional??

Dear All
I like to understand from the fellow HR professionals, how do they evaluate a Software Engineer or IT Professional? What are the parameters that they use?
I am looking for objective parameters (Something that can actually be calculated) and not subjective parameters such as behaviour, team-management, attitude, knowledge etc.
Kindly share.
Regards
Sanjeev Himachali

1. Will he stay atleast for 2 years?
2. Is there a scope for a person to adopt new technology?
3. Is there a scope for devloping a person?
4. Will he be suitable to company's environment?
5. Can he technically take forward the company?
.. and similar questions.
-hiren

His skills, his past experience, his ability to understand things and how fast he can pick up things