18 Across: Just an early sign of life to come - as you might be expecting! It's have 7,8 letters. ???N?N?S?C?N?S?
27 Across: Then, run to act out a double-crossing runaway. It's have 8 letters. T?R?C?A?
1 Down: Tried-and-true evidence, apparently, but there'll be no hearing if so. It's have 10 letters. ?O?N?P???F