can witness
Regular verb: witness - witnessed- witnessed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can witness
you can witness
he can witness
we can witness
you can witness
they can witness 	I can be witnessing
you can be witnessing
he can be witnessing
we can be witnessing
you can be witnessing
they can be witnessing	I can have witnessed
you can have witnessed
he can have witnessed
we can have witnessed
you can have witnessed
they can have witnessed	I can have been witnessing
you can have been witnessing
he can have been witnessing
we can have been witnessing
you can have been witnessing
they can have been witnessing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I cannot witness
you cannot witness
he cannot witness
we cannot witness
you cannot witness
they cannot witness 	I cannot be witnessing
you cannot be witnessing
he cannot be witnessing
we cannot be witnessing
you cannot be witnessing
they cannot be witnessing	I cannot have witnessed
you cannot have witnessed
he cannot have witnessed
we cannot have witnessed
you cannot have witnessed
they cannot have witnessed	I cannot have been witnessing
you cannot have been witnessing
he cannot have been witnessing
we cannot have been witnessing
you cannot have been witnessing
they cannot have been witnessing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I witness?
can you witness?
can he witness?
can we witness?
can you witness?
can they witness? 	can I be witnessing?
can you be witnessing?
can he be witnessing?
can we be witnessing?
can you be witnessing?
can they be witnessing? 	can I have witnessed?
can you have witnessed?
can he have witnessed?
can we have witnessed?
can you have witnessed?
can they have witnessed? 	can I have been witnessing?
can you have been witnessing?
can he have been witnessing?
can we have been witnessing?
can you have been witnessing?
can they have been witnessing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I not witness?
can you not witness?
can he not witness?
can we not witness?
can you not witness?
can they not witness? 	can I not be witnessing?
can you not be witnessing?
can he not be witnessing?
can we not be witnessing?
can you not be witnessing?
can they not be witnessing? 	can I not have witnessed?
can you not have witnessed?
can he not have witnessed?
can we not have witnessed?
can you not have witnessed?
can they not have witnessed? 	can I not have been witnessing?
can you not have been witnessing?
can he not have been witnessing?
can we not have been witnessing?
can you not have been witnessing?
can they not have been witnessing?