We French people are amazed by the reports from the international press about our urban violence crisis. Hey folks, France is not under fire !
I live in Lyon, and work as a teacher in one of the most violent districts in France (Les Minguettes, in Vénissieux, south of Lyon, which is our local South Bronx LOL)
Yes hundreds of cars burn every night in the country, but 95% of the violence is located in these areas where you wouldn't go at any time unless you have a good reason to. (unfortunately I have one : I work there)
Two days ago we had a major black-out in Lyon (half of the city was out of electricity for a couple of hours) because of malicious activity in an electric center and yes, I was a bit worried and didn't leave the window to make sure my car wasn't burning. But honestly, worrying about a trip to Paris, especially a sportsman's trip is a bit ... stupid.
The worst thing that could happen to Jeffrey, IMHO, is to come back home without the gold.
Edit : yes, the train running from the airport to Paris (RER B) crosses unsafe areas. It's safer to take a shuttle. (the unsafe areas are concentrated in the NE of Paris : [Seine St Denis, 93 department] not the SW)
STL_Blues_fan, Saint-Denis is not that touristic although what you mentionned is true. It's known as an unsafe area. I wouldn't go there at night at any time of the year. Anyway, keep in mind that the violence we see these days only happen after dark.