The other two examples including are both helpful in adding valuable information.

For example, it's good to point out that the punctuation of the source is less than helpful, and we should be mindful not to copy that comma for comma into the target.

In addition, that fact that the officer in question was on duty, not "de franco."

That said, there is something that doesn't jive for me, and that's the use of "exercise." To "exercise duties" doesn't sound like a good collocation to me. A common collocation for "exercise" is to "exercise a right." Yet for "duties" I think the more appropriate word would be "perform."

I'll support this assertion with the following:

If you Google "perform duties" without quotes, that is not the exact phrases you get 108,000,000 hits, compared to "exercise duties," which renders 944,000. If you restrict it to the exact phrase, "perform duties" gives you 370,000 compared to 25,300 for "exercise duties."

That's point number one.

Point number 2: If you look up "funciones" in Thomas West's Spanish-English Dictionary of Law and Business, the example sentence uses "perform duties," not "exercise duties.": Las funciones de los miembros del Consejo serán gratuitas -> The Board Members shall perform their duties without compensation.

I've added a couple links with copious reiteration of "performance of duties.

Hope this helps!