New York attorney record · Judicial Dept 1
Thomas D. O'Brien
Columbia University alumna, admitted to the New York bar in 2003, registered office in Sunnyvale, CA. This established record's status, address, and registration history come straight from the NY Office of Court Administration.
- 2003
- Admitted
- 23
- Years in bar
- 4154688
- NY reg #
The record in one line
Thomas D. O'Brien appears in the New York attorney register with a current status of "Due to reregister within 30 days of birthday", on record since 2003 - an administrative designation rather than discipline, but confirm current standing with the state bar.
- 23 yrs
- since first admission to the bar
- Pending-renewal
- current bar status: "Due to reregister within 30 days of birthday"
- #21 of 66
- by tenure in Sunnyvale office peers
- Law school
- Columbia University
Data updated September 2026
What this profile tells you
Bar status & tenure
Thomas D. O'Brien is registered as bar number 4154688 with the New York bar authority, carrying a current status of "Due to reregister within 30 days of birthday", a routine periodic-renewal reminder, not discipline. Registration is recorded within Judicial Department 1, the appellate division overseeing this attorney's home district.
Practice context & education
Practice address is listed under Illumio, Inc., located in Sunnyvale, CA, ZIP 94085. Educational background: COLUMBIA UNIVERSITY.
State context & due diligence
A "Due to reregister within 30 days of birthday" status falls outside the New York bar's active cohort for now. The breakdown below shows what share of the register that represents.
Tenure among Sunnyvale, CA office peers
Thomas D. O'Brien is toward the newer end of Sunnyvale, CA's NY register cohort: #21 of 66 by years since admission. See the Sunnyvale attorney directory .
- Local rank
- #21
- City cohort
- 66
- Local percentile
- 30th
- Admitted
- 2003
Nearest tenure peers in Sunnyvale
- Philip Lee Rothenberg admitted 2003 · 23 yr
- Gonzalo Ruiz San Sebastian admitted 2002 · 24 yr
- Emily Suhjean Chang admitted 2001 · 25 yr
- Catalin Cosovanu admitted 2005 · 21 yr
How local rank is computed
Rank uses years since NY-bar admission among non-deceased registry rows that list the same office city and state, a local placement, not a statewide claim. Source: NY Office of Court Administration Attorney Registration · as of September 2026. Derived local rank, not published upstream.
How Thomas compares to fellow Columbia University alumni
Among the 1,229 Columbia University graduates in the New York register, Thomas D. O'Brien is longer-tenured than 12%.
23 years vs. Columbia University alumni
Years since admission - 1,229 NY-registered alumni of this school
23 Top 88% higher than 12% of 1,229 fellow alumni
Each bar is a band; taller bars hold more fellow alumni. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source NY Office of Court Administration, Attorney Registration · September 2026
The 2003 admission class today
Of the 8,250 attorneys admitted to the New York bar in 2003, 83.9% are still "Currently registered" today, above the statewide average across all admission years.
Professional Details
- Status
- Due to reregister within 30 days of birthday
- Registration Number
- 4154688
- Year Admitted
- 2003 (23 yrs · senior)
- Judicial Department
- 1
- Next Registration
- Dec 2025
Location & Contact
- Company
- Illumio, Inc.
- City
- Sunnyvale, CA
- ZIP Code
- 94085
- Phone
- (646) 675-7019
Education
COLUMBIA UNIVERSITY
Status Distribution Across the New York Bar
Thomas D. O'Brien's current status, "Due to reregister within 30 days of birthday", places this record outside the 67.2% of the 432,625-attorney New York register currently marked active.
Full statewide breakdown & source note
Source: NY Office of Court Administration, Attorney Registrations. Status counts reflect the latest reporting cycle. Bar status confirms registration only; it does not imply competence, specialty fit, or freedom from complaints.
Near-tenure Columbia University alumni
Fellow alumni on the NY register whose admission year is closest to 2003 (excluding same-firm colleagues above).
Same admission year (2003), other cities
NY-registered attorneys admitted in 2003 whose listed office city differs from Sunnyvale, a vintage cohort, not a neighborhood list.
Nationwide attorneys with similar admission year or city registry density
Two non-geo peer axes for Thomas D. O'Brien: closest NY bar admission year outside CA, and closest out-of-state office cities by how many NY-registered attorneys they list (~67 here). Distinct from same-firm, fellow-alumni, and same-year other-city strips above.
Similar admission year (~2003)
Counts come from the NY State Office of Court Administration registration extract; peers are not a competence or practice-area ranking.
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Thomas D. O'Brien is currently listed as "Due to reregister within 30 days of birthday", treat that as a registration fact to confirm, not a verdict on quality.
Frequently Asked Questions
Where is Thomas O'Brien licensed?
Thomas O'Brien is licensed to practice law in New York.
When was Thomas D. O'Brien admitted to the bar?
Thomas D. O'Brien was admitted to the bar in 2003.
Where did Thomas D. O'Brien go to law school?
Thomas D. O'Brien attended COLUMBIA UNIVERSITY.
What company does Thomas D. O'Brien work for?
Thomas D. O'Brien is associated with Illumio, Inc. in Sunnyvale, CA.
Is Thomas D. O'Brien in good standing?
Not currently, Thomas D. O'Brien's listed status is "Due to reregister within 30 days of birthday", not active standing. Confirm current status with the state bar.
Cite this page & disclosure
Sourced from the NY Office of Court Administration, informational only, not legal advice. Full disclosure.
Read our methodology - how this data is sourced, computed, and verified.