nemo judex in causa sua (rule against bias)

 No-one is judge in his own cause. It is also called shortly as "nemo judex". It is made of following latin words:

• nemo = nobody
• iudex/judex = judge
• in causa = in case
• sua = own

A judge cannot have any, or fairly suspected to have any, bias or prejudice or self-interest in the case. If an interest is proved at any point causing the breach of natural justice, then the proceedings are quashed, any judgments passed are rendered invalid and a fresh hearing is started. It embodies the basic concept of impartiality.

The hard part here is how to prove the bias? An influential person will always try to attack judges alleging bias until she gets a favorable judge. Judges are normally expected to not take up cases in which they are biased.

There are three forms of bias:

1. Actual bias - Where it is actually established that a decision-maker was prejudiced in favour of or against a party. However, in practice, the making of such an allegation is rare as it is very hard to prove.

2. Imputed Bias - Where it can be inferred that a judge will gain something if judgment goes in favor of one party. Eg. judge holding shares in a company and outcome affects share price. Judge related to parties etc. or holding company is owned by relatives etc

3. Apparent bias - where a judge is not a party to a matter and does not have an interest in its outcome, but through her conduct or behavior gives rise to a suspicion that she is not impartial. To determine this, "real likelihood of bias" and "reasonable suspicion of bias". 

• The "real likelihood of bias" is concerned with the possibility, not probability, of bias. "whether the fair-minded and informed observer, having considered the facts, would conclude that there was a real possibility that the tribunal was biased"
• The "reasonable suspicion of bias" test asks whether a reasonable and fair-minded person sitting in court and knowing all the relevant facts would have a reasonable suspicion that a fair trial for the litigant is not possible.
• Both the tests are similar and should lead to similar outcome
  

Noted Judgments:

5-judge Bench of the Calcutta High Court to continue hearing CBI’s applications in #Narada scam case. Solicitor General Tushar Mehta for CBI addressed the Bench on principles of bias and perception of common man invoking nemo judex. Dr. AM Singhvi replied that "The mobocracy argument of CBI proceeds on a fundamental fallacy. Each judgment cited by them is based on Nemo Judex principle, which does not even arise in this case. It is totally inapplicable."

Open Qns:

1. How does it apply to police investigations?

    A noted case is of Dr Dhawan, refer this article.

Ref.

1. https://en.wikipedia.org/wiki/Natural_justice