Dr. Joy, an experienced physiotherapist, is preparing a presentation for a physiotherapy conference. He would like to include a real case study to illustrate an important point about the effectiveness of a specific technique. During the presentation, Dr. Joy mentions identifiable details and displays images of a client he treated, without having obtained formal authorization from the client or their legal guardian. Dr. Joy believes that using this information will enrich the presentation and promote the technique. Based on ethical standards for physiotherapists, which of Dr. Joy's actions is prohibited?