In this construction, at serves no real purpose in written English. In spoken English it serves as a speech marker, but that convention does not translate to written English. More effective technical writers, then, will eliminate at in phrase constructions involving where.
That means that the example sentence in the cropped graphic above is less effective. A more effective version could read like this:
Our team obtained the evidence from the consultant at his office.
In any case, avoid unnecessary words in your writing. Ax the at in where … at. Tighter writing usually makes for more effective writing, and that will produce a more effective image of you and your brands.