I do not rely on others to develop business cases while working with my clients. I take full accountability for their development as I understand how important the justification of business need is and how scare organizational resources are.
When I develop a business case, I clearly define the need, show current and future state, alternatives to get to the future state, ROI, Risk Analysis along with success criteria. I also ensure that assumptions are realistic with impacts if they are not true.
I never sell a business case to my sponsors, I provide sound analysis and leave investment decisions to the organization.
In the end, in most cases we have helped organizations get to the desired future state.