Here's why:

* Material: CD cases are usually made of polycarbonate plastic, which is a good insulator.

* Lack of Conductivity: Insulators resist the flow of electricity. Polycarbonate has very low electrical conductivity, meaning it doesn't allow electricity to flow through it easily.

However, there are a few things to consider:

* Moisture: If a CD case gets wet, it can become more conductive, as water can act as a conductor.

* Specific Type: Some CD cases might be made from different materials, which could have different insulating properties.

In general, though, a CD case is a safe bet to use as an insulator in most situations.