You may not like the idea of more work, but I'd really suggest you also ought to do a check of the other technician also. You'd basically be trying to compare if the difference between your check and the questioinable techinician is significantly different from the difference between your check and the "good" technician.
You may also want to throw some known bad parts into this "test" to see if both can detect bad parts.
It's possible you could also look at past data from the two technicians, and check using p-chart control charts or binomial tests to see if their failure rates for "bad parts" are statisically the same or different. If we assume all parts have an equal chance of being bad, then both inspectors should have the same failure rate for bad parts, within statistical uncertainty levels.
You may also want to throw some known bad parts into this "test" to see if both can detect bad parts.
It's possible you could also look at past data from the two technicians, and check using p-chart control charts or binomial tests to see if their failure rates for "bad parts" are statisically the same or different. If we assume all parts have an equal chance of being bad, then both inspectors should have the same failure rate for bad parts, within statistical uncertainty levels.