Can I legally ask an applicant to explain their credit history?

[John Kaspar]

So, had a applicant with a really awkward credit history but they hit all the other marks. Can I legally ask her to explain these or am I playing with fire?

(Landlord in MA) 

[John Underwood]

@John Kaspar I have told tenants that there are issues with their credit report that I am going to have to decline them over. I tell them if they would like to explain any of it that I will take the explanation into consideration.

Things like Divorce or Medical bills I would consider overlooking.