Regardless of the outcome of the trial, you find yourself in a difficult situation.
No matter what you said or did, you will be thrown in jail, and for some reason they let you keep your sword. If you were found not guilty, a pink bag will be waiting for you in the cell. Take it. Drink from the mug to regain your health, and save at the save point.
Wait... or Escape
You should wait for your execution. However, if you want more of a challenge, walk up to the bars three times to escape from your cell.
After Lucca joins, check the chest in the execution room (BronzeMail). Then go south to the next room, open the chest here (Mid Tonic), and free the guy who is trapped in the guillotine. Check on the guard for a Mid Tonic.
Whenever you see a guard, try to run behind him when his back is turned, and check on him to knock him out. Then check on him again to get a Mid Tonic. If you don't knock out the guard, you'll have to fight him.
First, go west along the southern path, then go down the stairs. Keep going until you reach a room with shield monsters. If you center yourself between the two monsters and walk straight down between them, you won't have to fight them.
Get past the shield monsters, and go down the southwest staircase. You can go into your old cell and drink from the mug to heal up, and save your game.
Then, if you want some extra treasure and don't mind fighting to get it, go back to the shield monster room and go down the southeast staircase. Cross the bridge to reach the next area, then stay near the north wall, knock out the guard, and open the cell to find some chests (left: Ether; mid-left: Mid Tonic; mid-right: Mid Tonic; right: Ether). Then go back the way you came. Don't worry about the Omnicrone that you have to fight. It is weak and almost always misses.
Go back up to the shield monster room, and go back up the northeast staircase. Cross the bridge to reach the next area. Knock out the guard, then when the path splits, go north, then west, knock out the guard, and go up the stairs. Cross the bridge and you will reach another shield monster room.
In this shield monster room, go down the southwest staircase first, open the first cell, and open the chest (Shelter).
Back in the shield monster room, go up the northwest staircase. Go into the open cell and out the hole. Go all the way to the right of the ledge and climb down, then go to the gap to the left and climb down, then go to the left side and climb down, then go right to go through the hole. Open the chest (Shelter), then go to the left and check on the hole in the floor to climb down. Open the chests (left: 1500G; right: Lode Sword), then to climb back up, just check on the north wall to the left of the window.
Go back the way you came to reach the shield monster room, then go up the northeast staircase. Keep going up and follow the straightforward path.
Check on the collapsed guy for five Mid Tonics. Read the note if you wish, then save the game and go north up the stairs. Then keep going left.
Kill the Tank Head first, then the Grinder wheel, and then the Dragon Tank body. Keep your HP above 50. Just use regular attacks. Have Lucca heal.
Go west and through the door. Open the chest to get a Shelter, then keep going down the stairs until you see more guards. Run south and try to get out of the castle. There will be a cutscene.
Once you're outside of the castle, run east. There will be a cutscene. After the cutscene, check on the Gate and you will eventually reach a new area.