beta
Its only natural for the duke to think that way because its true that Jace's identity is still yet mystery for hin even though he knew pieces of Jace's school life and job life. In the past its very hard to identify the culprit. Jace was also the last person whom they saw with the duke's brother. So like any other kidnapping cases Jace is a primary suspect. There's still no information about the kidnapping so its normal to suspect anyone even those who are likely to be innocent.