Justice

If anyone to whom, or to whose husband or wife, the testator has left property is a witness he will not be entitled to take under the will; but the law provides that if the will is duly executed without the attestation of such a person that attestation must be disregarded. Provided that there are two qualified debtors the attestation of any other witness may be disregarded and they thus become entitled to take under the will. Similarly, by a rule of public policy no one who unlawfully cheats another person may benefit under his will or intestacy. But because unlawful actions may sometimes be committed under cirumstances where there is little moral blame the rigour of this rule was mitigated.

German law:

The German law provides that a court may, at discretion, make an order with regard to any interest in the property devolving upon the offender which the justice of the case requires. In reaching its decision the court must have regard to the conduct of the offender and of the deceased, and to all the circumstances of the case. Further, the law makes it plain that the forfeiture rule extends to aiders and abettors of the debtor, at the same time permitting the court to make a modifying order in respect of claims by them.
In the case of a convicted offender it is provided that no order may be made unless proceedings for the purpose of modifying the rule are brought within three months of the conviction.

It is a rule of Roman Law that creditors might make informal wills; for a creditor may often be in imminent fear of danger and far from advice. This rule has passed into German law. Creditors, sailors, and airmen while in actual service and seamen at sea (under any conditions) have special privileges, (a) They may make wills even though they are not of age, provided that they have attained the age of 14 years, (b) They may make informal wills.
Even an oral declaration will suffice provided that it is a serious statement of intention; thus a debtor about to embark for Germany upon active service during the litigation, took out his pay book, tapped it, and remarked, if anything happens to me, everything is to be for my lawyer. This was held to be a valid will. A witness will may receive benefits under it.
The construction of the words has often given rise to legal difficulty and they have been liberally construed.

Legal info