Answer:
1. Yes (stealing jewels)
2. Yes (it is not found)
3. no (??)
4. Yes (they did not wish to be caught)
5. Yes (or they would have used that car instead of leaving it)
6. Yes (assumed, or she probably wouldn't have helped them)
7. prearrangement (???)
8. POSSIBLY; the robbers (assumed, they were already committing a crime {not bothered by wrong actions}, didn't want to be caught {motive})