by association 的字面意思是“通过联想或联系”。

guilt / guilty by association 属惯用搭配，意思是“牵连犯罪”“因为有关联而有罪”。

prove guilt by association 的意思是“证明有牵连犯罪行为”，即通过相关人员的犯罪事实来推定某人有罪。

Lawyers said the charges were an attempt to prove guilt by association. 律师说这些指控是企图要证明有牵连犯罪行为。

又如：

Some were judged guilty by association. 有些人被判有牵连犯罪行为。

再举一个相关的用法：

They were my family not by blood but by association. 他们是我家的人，不是因为有血缘关系，而是由于有姻亲关系。