Your colleague needs to obtain professional liability insurance, which often is called errors and omissions insurance. This insurance protects the consultant in cases where he/she makes a decision or offers assistance that causes real or perceived damage to the client. It is fairly expensive, but it is required by many clients. It should be considered a "cost of doing business" for consultants. Pricing is based on the consultant's experience (a lengthy questionnaire is submitted during the application process, and the number of consultants working at the firm (every employee is covered in the process of obtaining the insurance). Consider it to be the consultant;s equivalent of malpractice insurance.