... There is no question that, in legal terms, marriage ends on death. Both parties agree that this is the case, the law is clear on this point and it is acknowledged in subsection 248(23). Immediately following Mr. Juba’s death, Ms. Kuchta was no longer married to him.
He surveys other uses of "spouse" in the ITA, in the context of death, e.g., 146(8.91), (8.8), (8.2) 70(6), 72(2). Here, though, is a surprising comment that Justice Graham makes on the scope of s. 160:
Transfers on death:
 There is nothing in the Act that would indicate that Parliament intended to give relief from subsection 160(1) to transfers of property on death. In fact, the opposite is true. Paragraph 160(1)(c) causes subsection 160(1) to apply to transfers to anyone who was dealing at non-arm’s length with the transferor. Paragraph 251(1)(b) deems an estate to deal at non-arm’s length with any beneficiary of the estate. The combined effect of these two paragraphs is that anyone who receives property under a will is caught by subsection 160(1) whether or not they would otherwise deal with the deceased at arm’s length. Thus, for example, a charity that receives a bequest from a tax debtor under a will is caught by subsection 160(1) despite the fact that that same charity would not be caught had the deceased made the gift during his or her lifetime.
 In summary, there are two different meanings of the word “spouse”: one legal and one colloquial. A contextual analysis shows that Parliament has used both the legal and colloquial meanings in provisions of the Act involving transfers of property on death. This use of the both meanings demonstrates that there is textual ambiguity in the meaning of the word “spouse” in subsection 160(1). Given that ambiguity, it is appropriate to give weight to the purpose of the subsection. The purposive analysis points strongly in favour of an interpretation of “spouse” in subsection 160(1) that includes widows and widowers. Accordingly, I find that the word “spouse” in subsection 160(1) includes a person who was, immediately before the tax debtor’s death, his or her spouse.
So, Mrs. Kuchta was liable for her deceased spouse's tax debts.
Kuchta v. The Queen 2015 TCC 289 (Graham)