We need a new team leader and have two internal applicants, one of whom is pregnant. She's not the best candidate, but do we need to prove that our decision is not related to the fact that she's pregnant? If so, how should we do this?
It is important to be able to demonstrate clearly that you did not treat someone less favourably because of a "protected characteristic". Protected characteristics are defined in the Equality Act 2010 – in this case the protected characteristic would be pregnancy.
It is essential that you produce selection criteria that do not put the pregnant employee at a disadvantage when compared with her fellow employee. This would include performance (appraisals are a good tool, providing you disregard anything related to her pregnancy), qualifications and attendance (again, disregard any pregnancy-related absence).
Essentially, anywhere that you can produce data to support your decision is helpful as statistics will help to prove that you have been objective in carrying out your selection process.
In short, you need to be able to show that you applied exactly the same set of criteria to both candidates and that you selected the one that provided the 'best fit'.
This would be the same with any candidates, of course, even if a protected characteristic – pregnancy or any other – was not involved.
Measurable criteria, consistency and transparency are absolutely essential.