Although the case law is somewhat unclear, the conservative position is that an unwitnessed trust deed is invalid because it has not been duly executed. The case law suggests that a deed needs to be witnessed and signed contemporaneously for it to be valid.
There are a number of potential options to address this type of situation, depending on the exact factual matrix and level of protection the client is wanting to achieve. As always, View can provide an upfront scope of work and guaranteed fixed price to assist, upon request.