EXHIBIT 5.1

	355 South Grand Avenue
	Los Angeles, California 90071-1560
	Tel: +1.213.485.1234 Fax: +1.213.891.8763
	www.lw.com
	FIRM / AFFILIATE OFFICES
	Abu Dhabi	Moscow
	Barcelona	Munich
	Beijing	New Jersey
	Brussels	New York
	Chicago	Orange County
	Doha	Paris
	Dubai	Riyadh
June 21, 2010	Frankfurt	Rome
	Hamburg	San Diego
	Hong Kong	San Francisco
	Houston	Shanghai
	London	Silicon Valley
	Los Angeles	Singapore
Guidance Software, Inc.	Madrid	Tokyo
215 North Marengo Avenue	Milan	Washington, D.C.
Pasadena, California 91101

Re: Registration Statement on Form S-8 for Guidance Software, Inc.

Second Amended and Restated 2004 Equity Incentive Plan

Ladies and Gentlemen:

We have acted as special counsel to Guidance Software, Inc., a Delaware corporation (the “Company”), in connection with the proposed issuance of up to 2,086,439 shares of common stock, $0.001 par value per share (the “Shares”), to be issued pursuant to the Company’s Second Amended and Restated 2004 Equity Incentive Plan (the “Plan”), pursuant to a registration statement on Form S-8 under the Securities Act of 1933, as amended (the “Act”), filed with the Securities and Exchange Commission (the “Commission”) on June 21, 2010 (the “Registration Statement”). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement, other than as expressly stated herein with respect to the issue of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the Delaware General Corporation Law, and we express no opinion with respect to any other laws.

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, when certificates representing the Shares in the proper form have been manually signed by an authorized officer of the transfer agent and registrar therefor, and have been issued by the Company against payment therefor (not less than par value) in the circumstances contemplated by the Plan, assuming in each case that the individual grants or awards under the Plan are duly authorized by all necessary corporate action and duly granted or awarded and exercised in accordance with the requirements of law and the Plan (and the agreements and awards duly adopted thereunder and in accordance therewith), the issue and sale of the Shares will have been duly authorized by all necessary corporate action of the Company, and the Shares will be validly issued, fully paid and nonassessable.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ Latham & Watkins LLP