Another form of physical destruction, shredding may be the most secure and cost-effective way to destroy electronic data in any media that contain hard drives or solid state drives and have reached their end-of-life. It's also very effective for optical drives, smartphones, tablets, motherboards, thumb drives and credit card swipe devices, to name a few.
Shredding is a great way to destroy data if you have a large data enterprise center or a large stockpile of old hard drives and media that you want to destroy. It's very secure, fast and efficient. Shredding reduces electronic devices to pieces no larger than 2 millimeters. If you work in a high-security environment with high-security data, shredding should be your number one choice as it guarantees that all data is obliterated.
https://dataspan.com/blog/what-are-the-different-types-of-data-destruction-and-which-one-should-you-use/

Separation of duties - is a means of establishing checks and balances against the possibility that critical system or procedures can be compromised by insider threats. Duties and responsibilities should be divided among individuals to prevent ethical conflicts or abuse of powers.