Exhibit 31

CERTIFICATION

I, Harry G. Mitchell, certify that:

1. I have reviewed this quarterly report on Form 10-QSB of Sontra Medical Corporation;

2. Based on my knowledge, this
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 report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all
material respects the financial condition, results of operations and cash flows of the small business issuer as of, and for, the periods presented in this report.

4. The small business issuer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 small business issuer
and 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 small business issuer, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Evaluated the effectiveness of the small business issuers disclosure controls and procedures and presented in this report our conclusions about the
effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(c) Disclosed in
this report any change in the small business issuers internal control over financial reporting that occurred during the small business issuers most recent fiscal quarter (the small business issuers fourth fiscal quarter in the case
of an annual report) that has materially affected, or is reasonably likely to materially affect, the small business issuers internal control over financial reporting; and

5. The small business issuers other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the small business issuers auditors and the
audit committee of the small business issuers board of directors (or persons performing the equivalent function):

(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 small business issuer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 small business issuers
internal control over financial reporting.

Date: May 15, 2007



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|/s/ Harry G. Mitchell                                                
|Harry G. Mitchell                                                    
|Interim Chief Executive Office, Chief Financial Officer
and Treasurer