Under the usage of der/die/das as a demonstrative pronoun, leo.org lists the usage of dessen/deren to mark ownership clearly. As an example, the site gives -
- Herr Müller geht mit Anton und seiner Schwester weg.
- Herr Müller geht mit Anton und dessen Schwester weg.
In the first sentence, "Schwester" can be either "Herr Müller’s" or Anton’s sister. In the second sentence, "Schwester" must be Anton’s sister, because "dessen" can‘t refer to the subject of the sentence "Herr Müller".
There is another sentence on the webpage, that I can‘t fit into this rule:
Er liebt nicht die Frau, sondern deren Geld.
Since there is no confusion between the masculine subject "er" and feminine "die Frau", I would have written "ihres Geld". I’m not sure why "deren" is being used here.