De testamentis et de his, qui testamenta facere non possunt: theses XL

By the same example as the insane person, the spendthrift prodigus one who squanders property, who has been forbidden from managing his own goods, is not permitted to make a will: if he does so, it is invalid by the law itself.

Due to a bodily defect or disease, the right to make a will is also denied to some.

For the mute and the deaf are forbidden from making a will, unless the former can express his judgment in writing, or the latter can articulate his will.

We understand the mute to be not only he who can speak nothing, but also he who speaks ἀσήμως inarticulately/without clear sound, not he who speaks ἀσαφῶς vaguely/obscurely.

A blind person is also not permitted to make a will unless he observes the form prescribed by the constitution of Justinian.

Others, besides those already mentioned, remain who are deprived of the ability to make a will by reason of a crime: such are heretics and those guilty of the crime of high treason, who lose the right to make a will even before their conviction.

The laws also forbid the last will of one who anticipates his punishment by a voluntary death, out of fear of future penalty, from being upheld.

Under canon law, usurers are also not permitted to make wills unless they have provided security for the unjustly extorted interest.

For the same clear reason, a person condemned for a libelous poem carmen famosum slanderous song or poem is prohibited from testifying.