Will I be sinful for concealing information from the judge for fear of accountability and imprisonment, and what is the expiation for that?

It is not permissible to conceal testimony, for it is a grave matter, as Allah, the Most High, says: "And uphold testimony for Allah," and "And do not conceal testimony. And whoever conceals it - his heart is sinful." It is obligatory to render it, especially if it is specifically required or if withholding it would lead to the loss of a right for a Muslim, unless the witness fears unjust harm to himself, his property, or his honor. In such a case, he is not obligated to render it, based on the words of Allah, the Most High: "Let no scribe be harmed or any witness," and the saying of the Prophet, peace and blessings be upon him: "There should be no harm nor reciprocating harm." It is not obligatory to give testimony if the ruler is unjust. However, if the harm is deserved, then it is obligatory to give testimony, otherwise the witness would be held liable for the rights that were lost.