I'm having a hard time believing the car was parked in the path, Here's why.Interesting.
Just building on that...how long would the killer need? While it's impossible to be precise, in my opinion it could have been as little as 20 minutes from when he parked the car to when he took off after the crime. That would be the minimum time. While that's a long time to have the car on the side of the road - it's not an eternity; especially if it was partially out of sight such as a little way down the cart path.
If it was, that grass was high enough where it would have been matted down from the tires. I would think LE would have brought that up at the first press conference, but they didn't till the second, and only mentioned a car possibly being parked "along BSR", not "in" the path.
I do think he could have pulled it off in 20 minutes, but I think he spent a lot more time then that, especially if you are with DeDee's belief that he was enjoying himself. From the looks of the burned area, it looked like the flames were fairly high, so it must have taken a while to build a fire that large. I'll say at least an hour. JMO.