A Testamentary Special Needs Trust is not a stand-alone trust; rather, it is a established through provisions in a person's last will and testament. This type of trust only comes into existence after the willmaker passes away, at which time the trust is also funded according to the instructions in the will.

     It is a type of Third Party Special Needs Trust, which means the funds within a Testamentary Special Needs Trust are protected and do not count as assets for Supplemental Security Income (SSI) and Medicaid purposes. Further, the trust is not required to pay back Medicaid for costs or services paid on behalf of the beneficiary. 

     However, there are some drawbacks to consider. For instance, a Testamentary Special Needs Trust does not avoid the probate process, which can delay access to the funds. Moreover, if grandparents or other family members wish to leave an inheritance or gift to special needs beneficiary through the trust, they cannot do so until the trust is officially activated upon the parent's death. Because of these complexities, it is important to consult with an attorney who can help determine the most appropriate type of trust to meet your family's specific goals and circumstances.