Two things set the investigation of Apple Inc. apart from the hundreds of other stock option backdating probes: The indispensability of the company’s CEO, and the fact that while both in-house lawyers and HR staff were involved with options grants, it’s the lawyers who are getting the most scrutiny.

With Apple’s fortunes tightly linked to its leader, Silicon Valley titan Steve Jobs, anything seen as jeopardizing his role at the company strikes intense fear into stockholders. That helps explain why Jobs took the risky step last week of talking to federal prosecutors and SEC lawyers to convince them of his innocence.