I don't know why you cannot use internal audits as evidence.
"A method, other than internal auditing, to ensure that a procedure is effectively implemented either a new or modified procedure is not taken into consideration."
You have a defined system is how. Your system has to define the process of initiating new procedures and how to change a procedure. The system has to address issues such as distribution and, where appropriate, training. Each company is different as are different type of procedures (by procedures I also encompass documents such as work instructions, etc.) in a company. Change the Scrap procedure (assuming a global procedure) and a lot of people have to be informed in some way.
This can be taken to extremes. In a wafer fab tests are given, shift change meetings are utilized, etc. In an basic assembly shop there are seldom tests and often no shift meetings. But - if your system is designed well (and works well) you can find plenty of evidence that you comply.
How do I know operators are using the most recent issue? You use a defined system which ensures removal of obsolete documents. I see no reason why you can't verify that the system is effective through internal audits, however. How do I know if a procedure was effectively implemented? What type of procedure are we talking about... If you implement a specific work instruction you can cite scrap resulting from operator error, as an example. If there are high scrap levels which can be traced to operator error and the error is determined to be the result of using an obsolete work instruction, your document update system may be broken (or they may have hidden cheat sheets which is another issue).
The point is, you have to look at your over all systems and consider outputs. You have to use some common sense here. You can't test everyone on every procedural change. Nor can you follow up on every procedural change to 'ensure' it is 'effectively' implemented.
And I sure would like other comments on my thoughts. I'm not very good with words.