Product documentation and configuration guides marked as internal, a record of Nadia's installations and training, her training certificates and any internal manuals she wrote, a letter comparing her knowledge with what is generally available, the corporate relationship records, and the customer contract governing onsite work.
Prove the knowledge with artefacts, and prove control with the contract
Two evidence sets do the work. The first shows specialized knowledge: internal technical documents that describe the system's configuration and integration, dated training records, a list of hospital commissionings Nadia led with her role in each, and a statement from her manager explaining what a new hire would have to learn and how long it takes. If she authored validation checklists or trained others, include those materials with her name on them. The second shows the offsite placement is legitimate: the equipment sale or service contract with the hospital, showing commissioning and training are deliverables of the sale rather than hourly labour; her employer's project plan for each site; and a description of who assigns, reviews and pays her. Add the qualifying-relationship documents and evidence both entities are operating. Together they answer the two questions that decide the case.
Hypothetical example: A textile-dye producer sends a formulation specialist to its U.S. operation. The documents should connect the person to the company’s processes without disclosing more trade-secret detail than necessary. A confidential appendix, access logs, training history, role comparison and a clear employer letter can show why the knowledge is unusual. Separately, payroll and tax evidence should prove the qualifying foreign employment. A generic job description or an undated letter makes it difficult to see whether the special knowledge belongs to the worker, the company, or neither.