Date: 201210
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Altimeter
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Human factors: Training / Qualification; Human-Machine Interface; Situational Awareness
Second reporter function: Captain; Pilot Not Flying
Anomaly: Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: I was the pilot flying. On approach into the airport we were given a crossing restriction of 14;000 FT. Upon passing 18;000 FT in our descent we ran the descent and approach checklist. The Captain and I both confirmed the altimeter settings were 30.12. As we approached the fix the altitude alerter sounded a thousand feet off of the Captain's side. At the fix we were given 12;000 FT and the Captain made a comment that the altitude did not capture. As I continued to descend the Captain instructed me to watch the autopilot and at 12;000 FT on his altimeter the airplane continued to descend. He instructed me to stop the airplane. I turned off the autopilot and hand flew it while we assessed the problem. I then transferred control to the Captain. I noticed my altimeter was reading 31.12. I adjusted my altimeter to the correct setting. ATC assigned us 11;000 FT about this time. I took back control of the aircraft after confirmation of the new altitude was received from ATC by the Captain. The Captain advised the Controller of a mishap and we continued the flight with no further instances. I feel that perhaps complacency was a factor. My habit of spinning the barometer setting knob instead of slowly turning it perhaps allowed the setting to jump so drastically. Normally the knob is hard to turn and the numbers change more slowly. Careful attention to all four numbers during the checklist rather than the final two could have prevented this error. Careful attention must be made each and every time a checklist is run regardless of the how many numerous of times it has been run in the past.I feel that more careful attention to all details of the checklist in the future will benefit me greatly. Double checking myself and the computer is a must to ensure safety and compliance. Taking my time and being more deliberate and diligent with the details of the checklist can prevent future mishaps. I also feel that stopping the airplane manually and overriding it more quickly before the automation is allowed to deviate from a clearance or when some information is in question. If something seems off chances are it is.


Second narrative: It was then that we noticed the First Officer's altimeter was set to 31.14; not 30.14. I have seen altitude selectors change without input; but never an altimeter setting. I can only assume we had missed the mistake on the descent and approach checklist.Threats that we could have had a loss of separation. Errors that the First Officer's altimeter was off and I didn't take over the aircraft soon enough to stop the descent.In the future; I will intervene sooner and more strongly. If I had taken control sooner I could have leveled the aircraft prior to going low.


Synopsis: An air carrier First Officer had a habit of setting his altimeter's barometric pressure by 'spinning' the set knob but inadvertently set a 1.00 difference causing an altitude deviation because the autopilot did not capture the MCP altitude.