The degree of independence avoids author bias and is often more effective at finding defects and failures.

There is several level of independence which is listed here from the lowest level of independence to the highest:
i. Tests by the person who wrote the item.
ii. Tests by another person within the same team, like another programmer.
iii.Tests by the person from some different group such as an independent test team.
iv.Tests by a person from a different organization or company, such as outsourced testing or certification by an external body. [Read more…] about What is independent testing? It’s benefits and risks