Answer:
Questioned document examiners can be called upon to investigate a variety of cases related to documents, including:
1. Forgery: when a document is suspected to have been forged or manipulated
2. Fraud: when a document is suspected to be fraudulent or to contain fraudulent information
3. Document alteration: when a document has been altered from its original form
4. Disputed wills: when the legitimacy of a will is in question
5. Anonymous letters or threats: when a document is suspected to be authored by an unknown person
6. Counterfeit currency: when a document is suspected to be counterfeit or fake, such as banknotes or checks
These are just some examples of the types of cases that may require the expertise of a questioned document examiner.