Departure from what? From your own calculation of the what the applicable guideline should be? From the Government's recommended guideline level in a proposed plea agreement? From the recommendation of the PSR? The judge is the only one who determines the correct guideline level. Any other recommendation is just that - a recommendation that carries only such weight as the judge thinks it is worth. Attorneys who practice in federal court are often able to convince the judge that the guideline level recommended by the Government or by the PSR is excessive. How excessive depends entirely on the facts of the case and what the Government or the PSR has proposed. A four-level difference may or may not be warranted. It is certainly not inherently impossible.
Keep in mind that departures are much less important than they once were because the guidelines themselves are now advisory only and the judge imposes sentence pursuant to Section 3553(a) and enjoys considerable sentencing discretion regardless what the guideline calculation may be.
These are just general observations and not advice about what you should do in your case. The only person who can advise you in your particular situation is your own attorney. I trust that you are represented by counsel. Approaching a federal criminal sentencing, like any other aspect of a federal criminal case, is definitely not a do-it-yourself project.
It depends on the facts and the judge listen to your attorney
My name is Stephen R. Cohen and have practiced since 1974. I practice in Los Angeles and Orange County, CA. These answers do not create an attorney client relationship. My answers may offend I believe in telling the truth, I use common sense as well as the law. Other state's laws may differ.. There are a lot of really good attorneys on this site, I will do limited appearances which are preparation of court documents it is , less expensive. However generally I believe an attorney is better than none, but many will offer a free consultation and a face to face meeting generally will be better, I like my clients to write a short one page history of the fact and questions they have prior to meeting with them, so nothing is forgotten.
Specific pleas under Rule 11(c)(1)(C) are rare but do happen. Please work with your attorney on this. Otherwise, you must have the case facts to back up a specific enumerated departure. If not, a variance is what you seek. Use the case facts t support a downward variance motion under 3553a to reduce your overall sentence, not just the advisory guideline calculation.
It looks like you are getting some very good answers here. One more point to keep in mind: if you are subject to a mandatory statutory minimum, the court cannot go below that unless the government files a motion for downward departure. This usually comes with substantial assistance to the government only. This cannot be forced by your attorney and the court cannot order the government to make the motion. Another way to escape application of a mandatory minimum is the safety valve exception for low level offenders with little criminal history. As stated, the sentencing scenarios should be thoroughly discussed with your attorney.
Details are important if fact essential to determining the sentencing guideline calculation. Downward departures are difficult to obtain even in the best of circumstances. Your question and your goal suggests that you and your attorney are engaged in negotiations with the government and that you have set -4 as the target. The viability of your goal(s) is best left to your experienced local federal criminal defense lawyer.
This answer/response is based on the information provided in the question asked and requires a much more complete context than is available in this public forum. Please do NOT use this answer/response to say or do anything regarding your situation. BEFORE you say or do anything consult with an experienced Federal and/or state criminal defense attorney in your jurisdiction who will listen to you and your concerns.