Sure you can over train. Here's a simple way to do it:
Deadlift for a set of 5, as much weight as you can handle, 5RM max
Deadlift for a set of 5, 95% of 5RM max
Deadlift for a set of 5, 90% of 5RM max
Deadlift for a set of 5, 85% of 5RM max
Deadlift for a set of 5, 80% of 5RM max
Deadlift for...