EXHIBIT 31.1

# CERTIFICATION

I, William P. Moffitt, certify that:

|1. |  | I have reviewed this quarterly report on Form 10-Q of i-STAT Corporation;
|-- |  | -------------------------------------------------------------------------

|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 operation and cash flows of i-STAT Corporation
               as of, and for, the periods presented in this quarterly report;
|-- |  | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|4. |  | i-STAT Corporations other certifying officers 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 i-STAT Corporation 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 i-STAT Corporation, 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 i-STAT Corporations disclosure controls and
               procedures and presented in this report our conclusions about the
effectiveness                of the disclosure controls and procedures, as of the period
ended June 30, 2003                based on such evaluation; and | 
| |  |  |  | -- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | 

| |  |  |  | c) | disclosed
in this report any change in i-STAT Corporations internal control
over financial reporting that occurred during the most recent fiscal
quarter that has materially affected, or is reasonably likely to
materially affect, i-STAT Corporations internal control over
financial reporting; and | 
| |  |  |  | -- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | 

|5. |  | i-STAT Corporations other certifying officers and I have disclosed, based
               on our most recent evaluation of internal control over financial reporting, to
               i-STAT Corporations auditors and the audit committee of i-STAT
               Corporation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 i-STAT Corporation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 i-STAT Corporations internal control
over financial reporting. | 
| |  |  |  | -- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | 

DATE:
August 12, 2003

/s/ William P. Moffitt

William
P. Moffitt President and Chief Executive Officer(Principal Executive Officer)