In a report concerning a mid-air collision between two aircraft, the NTSB blamed the ATC controller for lack of situational awareness.
https://www.ntsb.gov/_layouts/ntsb.a...16X60452&key=2
Mistakenly identifying the Cessna to the right of Eagle1 as N6ZP, the LC instructed the N6ZP pilot to make a right 360° turn to rejoin the downwind when, in fact, N1285U was the airplane to the right of Eagle1. (The LC stated in a postaccident interview that he thought the turn would resolve the conflict with Eagle1 and would help the Cessna avoid Eagle1's wake turbulence.) The N6ZP pilot acknowledged the LC's instruction and began turning; N1285U continued its approach to runway 26R.
KSDM is class D, just outside of San Diego's B airspace. The controller was overwhelmed with the amount of aircraft and was unable to handle the workload. Neither aircraft was fitted with TCAS.