I can witness you can witness he can witness we can witness you can witness they can witness
V-ing form
I can be witnessing you can be witnessing he can be witnessing we can be witnessing you can be witnessing they can be witnessing
Perfect
I can have witnessed you can have witnessed he can have witnessed we can have witnessed you can have witnessed they can have witnessed
V-ing perfect
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
I can't witness you can't witness he can't witness we can't witness you can't witness they can't witness
V-ing form
I can't be witnessing you can't be witnessing he can't be witnessing we can't be witnessing you can't be witnessing they can't be witnessing
Perfect
I can't have witnessed you can't have witnessed he can't have witnessed we can't have witnessed you can't have witnessed they can't have witnessed
V-ing perfect
I can't have been witnessing you can't have been witnessing he can't have been witnessing we can't have been witnessing you can't have been witnessing they can't have been witnessing
Interrogative form
Simple form
can I witness? can you witness? can he witness? can we witness? can you witness? can they witness?
V-ing form
can I be witnessing? can you be witnessing? can he be witnessing? can we be witnessing? can you be witnessing? can they be witnessing?
Perfect
can I have witnessed? can you have witnessed? can he have witnessed? can we have witnessed? can you have witnessed? can they have witnessed?
V-ing perfect
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
can't I witness? can't you witness? can't he witness? can't we witness? can't you witness? can't they witness?
V-ing form
can't I be witnessing? can't you be witnessing? can't he be witnessing? can't we be witnessing? can't you be witnessing? can't they be witnessing?
Perfect
can't I have witnessed? can't you have witnessed? can't he have witnessed? can't we have witnessed? can't you have witnessed? can't they have witnessed?
V-ing perfect
can't I have been witnessing? can't you have been witnessing? can't he have been witnessing? can't we have been witnessing? can't you have been witnessing? can't they have been witnessing?