<PAGE>
                                                                    EXHIBIT 31.2

                                  CERTIFICATION

            PURSUANT TO SECTION 302 OF THE SARBANES OXLEY ACT OF 2002

I, Dennis E. Valentine, certify that:

            1) I have reviewed this quarterly report on Form 10-Q of JMAR
      Technologies, Inc.;

            2) Based on my knowledge, this quarterly report does not contain any
      untrue statement of a material fact or omit to state a material fact
      necessary to make the statements made, in light of the circumstances under
      which such statements were made, not misleading with respect to the period
      covered by this quarterly report;

            3) Based on my knowledge, the financial statements, and other
      financial information included in this quarterly report, fairly present in
      all material respects the financial condition, results of operations and
      cash flows of the registrant as of, and for, the periods presented in this
      quarterly report;

            4) The registrant's other certifying officer and I are responsible
      for establishing and maintaining disclosure controls and procedures (as
      defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant
      and we have:

                  a) designed such disclosure controls and procedures, or caused
            such disclosure controls and procedures to be designed under our
            supervision, to ensure that material information relating to the
            registrant, including its consolidated subsidiaries, is made known
            to us by others within those entities, particularly during the
            period in which this quarterly report is being prepared;

                  b) evaluated the effectiveness of the registrant's disclosure
            controls and procedures and presented in this quarterly report our
            conclusions about the effectiveness of the disclosure controls and
            procedures, as of the end of the period covered by this quarterly
            report (based on such evaluation); and

                  c) disclosed in this quarterly report any change in the
            registrant's internal control over financial reporting that occurred
            during the registrant's most recent fiscal quarter that has
            materially affected, or is reasonably likely to materially affect,
            the registrant's internal control over financial reporting; and

            5) The registrant's other certifying officer and I have disclosed,
      based on our most recent evaluation of internal control over financial
      reporting, to the registrant's auditors and the audit committee of the
      registrant's board of directors:

                  a) all significant deficiencies and material weaknesses in the
            design or operation of internal control over financial reporting
            which are reasonably likely to adversely affect the registrant's
            ability to record, process, summarize and report financial
            information; and

                  b) any fraud, whether or not material, that involves
            management or other employees who have a significant role in the
            registrant's internal control over financial reporting.

                                                By:  /s/ Dennis E. Valentine
                                                     -----------------------
                                                     Dennis E. Valentine
                                                     Chief Financial Officer

August 11, 2003


                                       28