Not sure if there are others in this situation, game complete and a lot of crimes to finish before the platinum pops.
I ignored the crimes during my play-through, so there are a lot to get through.
Swinging around waiting for them to randomly spawn was something I wasn't looking forward to.
I ended up finding this
Basically, if you're swinging around all the time, the crimes don't have time to spawn.
All you need to do is get somewhere high so you can see crimes spawn and wait. Keep pressing R3 to scan for crimes.
Once the crime has spawned and you've completed the crime, move away from the area by a couple of blocks.
Then get somewhere high, wait and keep pressing R3.
I found this works really well and crimes normally spawn within 5-20 seconds.
If they don't just move a litter further away and try again.
This technique has sped up the grind towards the 'I Heart Manhattan' trophy dramatically.
Hopefully this helps someone out