Date: 201812
Local time of day: 1801-2400
Location: ZOA.ARTCC, CA
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZLC
ATC / advisory: Center ZOA
Second aircraft: A320
Reporter organization: Government
Reporter function: Enroute; Instructor
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Training / Qualification; Communication Breakdown; Situational Awareness
Second reporter function: Enroute; Trainee
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: I was training a developmental. Handoff from ZLA on Aircraft Z northwest bound and Aircraft Y northwest bound converging with Aircraft Z climbing out of FL340 to FL360. Handoff from ZLC on Aircraft X at FL360 westbound landing SFO. Developmental called ZLC and issued control instruction to descend Aircraft X to FL350 for traffic. ZLC controller said 'Sure but why don't you just take radar and descend him yourself; that's why you have control in the LOA.' or something to that effect. I explained a little of what should be obvious to another controller.Aircraft checked on frequency 10 miles inside our airspace level at FL360. R-side descended the aircraft and then asked if they were issued a descent by ZLC and they said no. Lateral separation appeared to be less than one tenth of a mile when the aircraft crossed. Having control for descent in the LOA does not mean we don't need to ensure separation before taking the handoff. In my opinion accepting 2 handoffs in conflict; especially that close; is negligence/dereliction of duty. ZLC should not question control instructions or play games like that when safety is a priority; which it always is.Ethics and professional standards training for anyone who does not believe safety is the first priority.


Second narrative: I am training on the D side in area east. Aircraft X and Aircraft Y were a red alert on the EDST. Aircraft X was an arrival into SFO and Aircraft Y was an overflight going [north]. I issued a control instruction to ZLC for Aircraft X to descend and maintain FL350 for traffic; to which he responded with you take the hand off then and you can descent him per the LOA. The problem with this is sometimes the aircraft do not get shipped in a timely manner and the conflict was going to happen pretty quickly once the airplane entered my airspace and as a trainee it is good for me to show my trainer I see the traffic and can make a decision on my own. He responded negatively to my control instruction then argued with my trainer on the line about why we didn't just move Aircraft Y for traffic. We waited for a few minutes to see if he would descend the airplane but it still showed 360. My trainer told me to take the handoff and show 350 in the data block which I did. The airplane checks on a little but later not having been issued the descent clearance. He had to be expedited down for traffic. Salt Lake should not complain when we issue control instructions for traffic. It is in the interest of safety when they don't comply.


Synopsis: ZOA ARTCC Controllers reported a loss of separation due to another Center not providing required separation prior to handoff.