How to use data from a colleague who retired in my thesis without commiting fraud or plagiarism A colleague of mine who worked on the same project retired one year ago. I would like to use some of the data he measured and reproduce some of his figures. He gathered the data while performing a routine analysis of our raw material e.g binding kinetics or adsorption isotherms. In general, nothing groundbreaking. Unfortunately, he did not publish the particular dataset. As a consequence, I cannot cite him.

How can I use that data without being accused of plagiarism or fraud. Of course, I will ask him for the permission to use that data.

Would you state that in the introduction or the figure legend? And what would you write?

EDIT:

I forgot to mention that I will write my Thesis as a monograph and publish it later.
As PatW says in a comment: the general correct action in this case is coauthorship. This gets a little bit trickier with a thesis, which does not typically allow coauthors per se. For the thesis, the thing you should do is give explicit credit where the data is introduced. If it corresponds with the practices of your field, you can also put in a citation to your colleague as an unpublished document or personal communication.

When you republish this material as a journal manuscript or other conventional form that allows multiple authors, however, your colleague should be amongst the set of coauthors.