For the source text click/tap here: Sanhedrin 28
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The Mishnah (27b) teaches that people who are closely related – by blood or by marriage – will be disqualified from testifying about one another. Thus a person cannot testify for or against his brother or his sister’s husband, similarly he cannot be a witness regarding a case involving his uncle, whether it is his mother’s brother or his father’s brother, or, for that matter his mother’s sister’s husband or his father’s sister’s husband.
Why are relatives limited in this way?
The Gemara quotes Devarim 24:16 as a pasuk that can be interpreted to serve as the source for this law.
We explore personal vs inherited responsibility.