Simple:
* My conscience wouldn't allow me to lie to her.
* Her conscience was clear, knowing she had done the right thing.
More complex:
* The weight of her actions sat heavily on her conscience, leaving her feeling guilty.
* The court found him guilty, but his conscience remained innocent.
* The lawyer appealed to the jury's conscience, urging them to consider the mitigating circumstances.
Figurative:
* The museum's collection spoke to his conscience, reminding him of the beauty and fragility of the world.
* The sound of the child's laughter awakened her long-dormant conscience.
Let me know if you'd like more examples!