<PAGE>

                                                                   EXHIBIT 10.16

                                 PROMISSORY NOTE

$320,314.83                                                 Seattle, Washington
                                                                   May 31, 2003

         For value received, the undersigned, jointly and severally, promise to
pay to Makena Commercentre II, LLC, or order, at 26522 La Alameda, Suite 285,
Mission Viejo, California 92691, or at such other address as holder may
designate, the aggregate principal sum of $320,314.83, together with interest
thereon from the date hereof at the rate of ten percent (10%) per annum.

         For June 2003 the undersigned shall make payments on this Note in the
amount of not less than $10,000 by June 30, 2003. For the period from July
through December 2003 the undersigned shall make payments on this Note in
cumulative amounts totaling not less than $25,000 by September 30, 2003 and not
less than $50,000 by December 31, 2003. Thereafter, the undersigned shall pay
this Note in cumulative amounts totaling not less than $25,000 by March 31 of
any calendar year in which this Note is unpaid; not less than $50,000 by June 30
of any such year; not less than $75,000 by September 30 of any such year; and
not less than $100,000 by December 31 of any such year, until this Note is paid
in full. Each payment shall be credited first to the interest then due and then
to the principal sum. All amounts under this Note shall in any case be due and
payable on any of the following: (a) completion of equity financing by any of
the undersigned, either alone or in combination with any other of the
undersigned, in the amount of at least $4,000,000; (b) close of escrow of sale
of the laboratory in the State of Washington owned by any of the undersigned;
(c) sale of substantially all assets of Pacific Biometrics, Inc., a Washington
corporation; or (d) not later than July 31, 2005.

         If any payment is not received within five business days after the date
it is due, the undersigned shall pay an additional amount of six percent (6%) of
the payment then due. In addition, if any payment is not received within five
business days after notice of default as provided in the Settlement Agreement
executed concurrently herewith, the holder hereof may, at its option, declare
the entire balance immediately due and payable.

         The undersigned may prepay all or any portion of such amount, together
with any accrued and unpaid interest thereon, at any time without premium or
penalty. Any such payment shall be credited first toward interest due and any
remainder toward principal. This note shall be construed according to California
law. If this note is collected by an attorney after default, either with or
without suit, the undersigned agrees to pay all costs and expenses of
collection, including a reasonable attorney's fee.

         The makers hereof waive presentment for payment, demand and notice of
dishonor and nonpayment of this note, and consent to any and all extensions of
time, renewals, waivers or modifications that may be granted by the holder
hereof with respect to the payment or other provisions of this note.

                                      -1-

<PAGE>

         Date: May 31, 2003

                                   PACIFIC BIOMETRICS, INC.,
                                   a Delaware corporation

                                   By:   /s/ Ronald Helm
                                         ---------------------------------------
                                         Ronald Helm, Chief Executive Officer

                                   By:   /s/ Timothy Wudi
                                         ---------------------------------------
                                         Timothy Wudi, Secretary

                                   PACIFIC BIOMETRICS, INC.,
                                   a Washington corporation

                                   By:   /s/ Ronald Helm
                                         ---------------------------------------
                                         Ronald Helm, Chief Executive Officer

                                   By:   /s/ Ronald Helm
                                         ---------------------------------------
                                         Ronald Helm, Secretary

                                   SAIGENE CORPORATION,
                                   a Delaware corporation

                                   By:   /s/ Allan Cochrane
                                         ---------------------------------------
                                         Allan Cochrane, Chief Operating Officer

                                   By:   /s/ Allan Cochrane
                                         ---------------------------------------
                                         Allan Cochrane, Secretary

                                      -2-