Judith Linzer, PHD
Judith Linzer, PHD is a Forensic Psychologist in Castro Valley, CA, registered under NPI 1487879268. This provider registers 5 separate taxonomy codes, which usually means they practise across more than one recognised specialty.
Getting there
The practice address on file is 20200 REDWOOD ROAD SUITE 2, Castro Valley, CA 94546. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| PSY9833 | CA | Forensic Psychologist primary |
| PSY9833 | CA | Psychologist |
| PSY9833 | CA | Clinical Psychologist |
| PSY9833 | CA | Clinical Child & Adolescent Psychologist |
| PSY9833 | CA | Family Psychologist |
This provider holds licence PSY9833 issued in CA. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
- Status
- Approved
- Provider type
- Order And Referring Only - Clinical Psychologist
- PAC ID
- 7012285935
- Enrollment ID
- I20170619001575
Medicare enrolment is recorded as approved under the provider type Order And Referring Only - Clinical Psychologist. Being enrolled means the provider can bill Medicare; it does not tell you whether they are currently accepting new Medicare patients. Call the office to confirm.
What Forensic covers
A psychologist whose specialty is characterized by activities primarily intended to provide professional psychological expertise within the judicial and legal systems. NUCC Health Care Provider Taxonomy, code 103TF0200X
All registered taxonomy codes
This provider registers 5 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 103TF0200X | Forensic Psychologist Forensic | PSY9833 | CA | primary |
| 103T00000X | Psychologist | PSY9833 | CA | |
| 103TC0700X | Clinical Psychologist Clinical | PSY9833 | CA | |
| 103TC2200X | Clinical Child & Adolescent Psychologist Clinical Child & Adolescent | PSY9833 | CA | |
| 103TF0000X | Family Psychologist Family | PSY9833 | CA |
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1487879268 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Apr 16, 2007 |
| Last updated | Sep 11, 2025 |
| Status | Active |
| Sole proprietor | No |
| Credential | PHD |
| Practice address |
20200 REDWOOD ROAD SUITE 2 Castro Valley, CA 94546 (510) 887-8819 Fax (510) 655-7974 |
| Mailing address |
4096 PIEDMONT AVE SUITE 320 Oakland, CA 94611 |
| Other identifiers |
075155
· Other |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 4 | 8 | 7 | 8 | 7 | 9 | 2 | 6 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 4 | 7 | 7 | 7 | 7 | 9 | 2 | 3 |
Sum = 72 · next multiple of 10 = 80 · check digit = 8 · actual last digit = 8
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.