What makes you think it would have been "pitch dark"? Aside from artificial light, the moon may have illuminated the night sky. (Full moon on the 24th.)
FWIW, I'd think a flashlight could draw unwanted attention & we don't know the perp's mode of transportation.
Having lived in both urban and rural areas, I can tell you the difference in walking at night is stark!! Even with moonlight. The Ramsey's neighborhood is very similar to the one I grew up in during my teens. It was near impossible to see at night without lights! It's not unusual to see people walk with flashlights to one anothers house or for joggers to wear jackets with reflectors. Heck dogwalkers usually head out with a flashlight often. So the intruder walking normally with a flashlight would not be a unique sight in that neighborhood.
we don't know the perp's mode of transportation.
That's actually a very critical question that needs to be answered in regards to the IDI theory. How did the intruder arrive and escape from the crime scene.
in regards to his modes of transportation
1. By foot - if the killer travelled by foot, that narrows down the suspect list. That gives us a very limited radius from which the killer could leave from his home and walk a reasonable distance to the Ramsey house. The killer then has to have resided in the Ramsey neighborhood at the time of the murder.
It also eliminates the kidnapping motive, since I don't think the killer would be that stupid to risk bringing a struggling little girl with him on foot. Unless his house was really close.
It could also be the answer as to why the killer never bothered to move the body. He had no transport. Perhaps also why he abandoned the kidnapping plan, as well
It would also explain why the killer chose to stay in the house for so long. Without the comfort of a car, he really didn't have a good place to wait in for the Ramsey's to come home.
2. (himself as the driver)
The killer couldn't leave his car in front of the ramsey residence, so he had to leave it somewhere within reasonable distance. This would also mean the car was parked in this location....the whole time from when the Ramseys left the house to when the killer escaped after the murder.
Course this brings up this point. If you have a car, why would you need to stay in the house till the Ramsey's arrived? It is much easier to stake out their place from inside the car. You can always leave every now and then to get food, supplies, etc. You have radio. Hell you can even write the ransom note from your car. And more importantly...if anything is awry...you can leave the vicinity quickly without anyone having any idea what you were up to!!!
To me it makes no sense to stay in the house if the intruder came by car.
To be honest, I think the IDI theory makes more sense if the killer arrived by foot from a location...that was VERY close to the Ramsey home.