Exhibit 99.1

Guidance Software Reports Record Q4 2010

PASADENA, Calif. – February 15, 2011 – Guidance Software, Inc. (NASDAQ: GUID) today reported financial results for the fourth quarter and year ended December 31, 2010.

Fourth quarter 2010 financial highlights, calculated in accordance with generally accepted accounting principles (GAAP) include:

On a non-GAAP basis, which excludes share-based compensation and amortization of intangibles, the company reported pre-tax net income of $1.2 million, or $0.05 per share, in the fourth quarter of 2010. For the fourth quarter of 2009, non-GAAP pre-tax net income was $190,000, or $0.01 per share.

For the year ended December 31, 2010, the company reported total revenue of $91.9 million, an increase of $17.0 million, or 23 percent, from $74.9 million in the year ended December 31, 2009.

On a GAAP basis, net loss was $4.6 million, or ($0.20) per share for the full year 2010, compared to a net loss of $13.9 million or ($0.60) per share, for the prior year. Non-GAAP pre-tax net income for the year ended December 31, 2010 was $1.6 million, or $0.07 per share, compared to non-GAAP pre-tax net loss of $8.1 million, or ($0.35) per share for the prior year.

Guidance Software President and Chief Executive Officer Victor Limongelli said, “Our fourth quarter performance marks a strong end to a record year. We have experienced solid demand for version 4 of EnCase® eDiscovery, which was released in late August, as well as our EnCase® Cybersecurity offering. Looking to 2011, we expect continued improvement in the eDiscovery and Cybersecurity markets and believe Guidance Software is uniquely positioned to benefit.”

Fourth Quarter 2010 Highlights and Recent Events

2011 Financial Outlook:

The company is initiating its guidance for the year ended December 31, 2011, as follows:

Conference Call Information:

The company will host a conference call today at 2:00 p.m. pacific time, 5:00 p.m. eastern time to discuss its quarterly results. Participants should call (877) 303-9850 (North America) or (408) 427-3732 (International) and should dial in at least 5 minutes prior to the conference call.

A webcast and replay of the call may also be found on the Internet through Guidance Software’s Investor Relations website at http://investors.guidancesoftware.com/events.cfm. Registered users may access this content over the Internet, and there is no cost to register. If you have not already registered, please do so at least 15 minutes prior to the start of the conference call.

An audio-only replay of the call will be available by calling (706) 645-9291, passcode 37713028, available from 8:00 pm eastern time, February 15, 2011, through midnight eastern time, February 23, 2011.

About Guidance Software:

Guidance Software is recognized worldwide as the industry leader in digital investigative solutions. Its EnCase® platform provides the foundation for government, corporate and law enforcement organizations to conduct thorough, network-enabled, and court-validated computer investigations of any kind, such as responding to eDiscovery requests, conducting internal investigations, responding to regulatory inquiries or performing data and compliance auditing - all while maintaining the integrity of the data. There are more than 30,000 licensed users of the EnCase® technology worldwide, the EnCase® Enterprise platform is used by over half of the Fortune 100, and thousands attend Guidance Software’s renowned training programs annually. For more information about Guidance Software, visit http://www.guidancesoftware.com.

Follow Guidance Software on Twitter at http://twitter.com/encase and on Facebook at http://www.facebook.com/guidancesoftware.

EnCase®, EnScript®, FastBloc®, EnCE®, Guidance Software^™ and Tableau^™ are registered trademarks or trademarks owned by Guidance Software in the United States and other jurisdictions and may not be used without prior written permission. All other marks and brands may be claimed as the property of their respective owners.

Forward Looking Statements:

This release contains forward-looking statements within the meaning of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Investors are cautioned that forward-looking statements in this release involve risks and uncertainties that could cause actual results to differ materially from current expectations.

There can be no assurance that demand for the company’s products will continue at current or greater levels, or that the company will continue to grow revenues, or be profitable.

There are also risks that the company’s pursuit of providing network security and eDiscovery technology might not be successful, or that if successful, it will not materially enhance the company’s financial performance; that the company could fail to retain key employees; that changes in customer requirements and other general economic and political uncertainties could impact the company’s relationship with its customers; and that delays in product development, competitive pressures or technical difficulties could impact timely delivery of next-generation products; and other risks and uncertainties that are described from time to time in Guidance Software’s periodic reports and registration statements filed with the Securities and Exchange Commission.

The company specifically disclaims any responsibility for updating these forward-looking statements.

GUID-F

Guidance Software, Inc.

Unaudited Condensed Consolidated Statements of Operations

(in thousands, except per share amounts)

Guidance Software, Inc.

Calculation of Pre-Tax Non-GAAP Income (Loss)

(unaudited)

(in thousands, except per share amounts)

Notes to Unaudited Condensed Consolidated Statements of Operations:

This press release and its attachments include the non-GAAP financial measures of income (loss) before income taxes excluding share-based compensation expense, restructuring costs, acquisition-related expenses and amortization of intangibles and non-GAAP income (loss) before income taxes per share excluding share-based compensation expense, restructuring costs, acquisition-related expenses and amortization of intangibles, which are reconciled to net loss and net loss per share, respectively, which we believe are the most comparable GAAP measures. We use these non-GAAP financial measures for internal managerial purposes, when publicly providing our business outlook, and to facilitate period-to-period comparisons. We describe limitations specific to each non-GAAP financial measure below.

Management generally compensates for limitations in the use of non-GAAP financial measures by relying on comparable GAAP financial measures and providing investors with a reconciliation of the non-GAAP financial measures only in addition to and in conjunction with results presented in accordance with GAAP. We believe that these non-GAAP financial measures reflect an additional way of viewing aspects of our operations that, when viewed with our GAAP results, provide a more complete understanding of factors and trends affecting our business. These non-GAAP measures should be considered as a supplement to, and not as a substitute for, or superior to, net loss and net loss per share calculated in accordance with GAAP.

Non-GAAP income (loss) is defined as follows: GAAP net income (loss) before income taxes excluding share-based compensation expense, restructuring costs, acquisition-related expenses and amortization of intangibles. Share-based compensation expense is recorded in accordance with the FASB Accounting Standards Codification (ASC 718) Compensation – Stock Compensation Topic (formerly Statement of Financial Accounting Standard No. 123R, “Share-Based Payment”) for equity awards to employees and directors. Management and the Board of Directors believe it is useful to review the supplemental non-GAAP financial measures, which excludes income taxes and expenses related to share-based compensation, restructuring, acquisition-related expenses and amortization of intangibles in evaluating the Company, its management team and business unit performance during a particular time period. Share-based compensation expense, restructuring costs, acquisition-related expenses, amortization of intangibles and income taxes are not the responsibility of operating managers and generally cannot be changed or influenced by management.

Additionally, we believe it is useful in measuring the Company’s performance to exclude expenses related to income taxes, share-based compensation expense, restructuring costs, acquisition-related expenses and amortization of intangibles because it facilitates comparability with prior period information.

Accordingly, management and the Board of Directors do not consider these excluded costs for purposes of evaluating the performance of the business, and they exclude such costs when evaluating the performance of the Company, its business units and its management teams and when making decisions to allocate resources among the Company’s business units.

Guidance Software, Inc.

Unaudited Condensed Consolidated Balance Sheets

(in thousands)

Guidance Software, Inc.

Unaudited Condensed Consolidated Statements of Cash Flows

(in thousands)