They will have had to have voluntarily excused themselves from the trial after it having commenced, or absconding prior to the trial beginning. So no they cannot be tried in absentia.
If they continue to evade then the judge may find them in contempt, however they are arguing their inability to comply with their attendance by being inadequately prepared (dubious reasoning).
If they continue to evade then the judge may find them in contempt, however they are arguing their inability to comply with their attendance by being inadequately prepared (dubious reasoning).