A person witnesses an event as a child (minor). When he reaches adulthood, can he testify about it in court?
Since a minor is initially disqualified, even if he becomes fully eligible later, the 'beginning was in disqualification' rule applies. He cannot testify. The exception is for specific Rabbinic-level matters only.
Question 2
Which of the following may an adult testify about based on childhood observations? (Rabbinic matters)
The Rambam lists recognizing the handwriting of one's father, teacher, or brother as one of the items an adult may testify about from childhood — because document validation is a Rabbinic requirement.
Question 3
A witness signed a document validly, but later became a robber (pasul). Can the document still be used?
If a witness's signature was validated in court before he became a robber, the document remains valid. If not, he cannot even testify to his own signature because a person disqualified for crime is suspected of forgery.
Question 4
A document has two witnesses who are relatives of each other. What is the document's status?
A document with only two witnesses who are relatives of each other is worthless (k'cheres) because of the invalid signatures within it, even if it was transferred before valid witnesses.
Question 5
A person is temporarily deaf-mute but then recovers. He knew evidence before he became deaf-mute and testifies after recovery. Is this testimony valid?
The rule is: if beginning and end are both in eligibility (kosher), even temporary disqualification in between does not invalidate. This applies to temporary deafness, blindness, or insanity that reversed.