Question

Why is a person's opinion about a situation not accepted as a scientific evidence

Answer 1

A person's opinion cannot be accepted as a scientific evidence in the court because scientific evidence either support or counter the scientific theories or hypothesis. Such evidence is interpretable according with the scientific methods. Mostly the results of scientific evidence is based on statistical analysis.

The main principle of scientific evidence: person's assumption on a relationship between observation and hypothesis will effect whether that percent take observation as an evidence.

Anecdotal and expert opinion: anecdotal evidence is a person's own personal experience. A expert's stand-alone opinion or that given a written news article. Both considered as a weak form of evidence. Without scientific studies backup them.

Therefore only a person's opinion is not considered as scientific evidence without a strong scientific studies.