At times a person may have one outstanding positive: worked for your main competitor, attended a university with a track record of doing well graduates, or even just comes from your native town.
If you also impulsively like the individual, it is tempting to be very influenced by this fact, and not pay as much as necessary attention to others that are not so appealing.
That is why when recording notes on each applicant make sure to record negatives as well as positives on the suitable pages.
When you evaluate your notes after the interview is finished, you will be better able to balance the pros and cons objectively.