Can diesel fuel be used in a jet engine?
It is as well to distinguish several different meanings of the word "can". Various of the answers here refer to those different meanings.
1. Will the engine produce thrust if you inject it?
2. Will the engine run for a substantial period of time, say a short flight, using it?
3. Will the engine run for a substantial period of time using it, without suffering major structural disadvantages or maintenance problems?
4. Is it allowed by some ops manual (through STC)?
You have to ask the same questions for the use of mogas in small-aircraft Otto-cycle engines. Caveats there have mostly to do nowadays with ethanol content and vapor lock. Given the lack of context of your question, I imagine the biggest caveat might well be temperature, since diesel fuel for ground use isn't really suitable for environments with the substantially low temperatures found at the flight levels at which jets are most efficient.
PBL