The CSRS FERS Handbook is the source for this information and Chapter 46 explains what you are looking for. Specifically, go to page 52, Part 46B3.3B.
https://www.opm.gov/retirement-center/publications-forms/csrsfers-handbook/c046.pdf
I am assuming you were a regular Law Enforcement Officer, not a Customs and Border Protection Officer, and that you are not currently in a secondary position. If I am correct, then your retirement will be computed using the 1% factor for all years and months of service, even the 12 years you had as a LEO because under FERS, you need to have 20 years as a LEO or FF to have the enhanced computation used to calculate your retirement. Consider it an all or nothing rule.
If you moved directly from a primary LEO position to a secondary LEO position, then LEO service continues, you are having the extra half percent taken out of your paycheck, and you will have the enhanced computation used to calculate your retirement.
You are not entitled to a refund of the half percent you paid into the retirement fund for the 12 years you worked as a LEO as you were properly classified at the time.
And finally, if you work until age 62 and have 20 or more years of total service, the formula increases to 1.1% x high-3 average salary x years/months of service instead of 1%. I hope I have addressed your questions and if not, please leave another message.
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Posted by Elaine Lumsden (Questions: 0, Answers: 386) 
