"Independent observers" refers to people who are not directly involved or influenced by a certain situation or event. They can provide an unbiased perspective, as they have no personal interest or stake in the matter. Full definition
Most independent observers would agree that the average quality of women MPs is higher than the average quality of male MPs. (totalpolitics.com)
In fact, if a husband was rated by independent observers as less attractive, the wife was feeling more loved and content in the relationship. (blogs.elenasmodels.com)
The same goes for independent observers from other countries and news organizations. (politics.stackexchange.com)