Working at Sentinel Offender Services | Glassdoor

Sentinel Offender Services Overview

Irvine, CA
201 to 500 employees
Company - Private
Security Services
$25 to $50 million (USD) per year
Helping people stay on the right path to a better life.

Since 1993, Sentinel Offender Services has been chosen by law enforcement agencies from across the country (i.e., courts, sheriff departments, probation and parole departments, etc.) as a trusted ... Read more

Mission: At Sentinel Offender Services, we are committed to helping create the best possible client management outcomes for our customers and the communities they serve. We demonstrate that commitment by offering high quality electronic monitoring hardware, innovative software platforms ... Read more

Company Updates

  • DAY REPORTING CENTERS | Making A Difference
    Sentinel has partnered with the Nevada Public Safety Division of Parole and Probation to open Day Reporting Centers in Las Vegas and Reno. Sentinel developed the Day Reporting Center Model to better assist our community corrections partners in their efforts to reduce recidivism by better preparing participants to successfully transition As a community-based resource, each DRC partners with state and local social services agencies and outreach organizations to provide participants with additional resources that actively support their efforts to get their lives back on the right path.In addition to providing court-mandated electronic monitoring and drug testing services, each DRC offers participants access to a host of services to help in their successful transition back into their communities. These include cognitive skills courses on subjects ranging from anger management to parenting and family values; and life skills courses in basic money management and employment readiness (e.g., résumé and cover letters, job search assistance, etc.).

  • JULIE HUNT, Director of Human Resources CELEBRATES 25 YEARS AT SENTINEL “Although I have hired more than 1,000 employees for Sentinel during my tenure, I have also worn many, many other hats. I have been responsible for everything from writing proposals to setting up payroll to coordinating the relocation of the company (twice). No two days were ever the same and loved every minute of it.
    “I was given a lot of responsibility but I was also given the opportunity to figure things out and learn. Bob (Contestabile) gave me the freedom and opportunity to grow with the company and learn many valuable lessons along the way. In fact, taking on new challenges—almost every day it seemed—and the lesson learned from those challenges helped turn me into the leader I am today. I’m really glad I took a chance 25 years ago, and I’m proud to be a part of this wonderful company!”

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Sentinel Offender Services – Why Work For Us?

About Sentinel Offender Services

Since 1993, Sentinel Offender Services has been a trusted partner of courts, sheriff departments, probation and parole departments, and other law enforcement agencies from across the country. We provide comprehensive case management and offender-management services.

Sentinel pioneered the first participant-funded program model in which all program fees are paid for by the participants directly, saving taxpayers millions of dollars in jail costs. At the time of enrollment into a participant-funded program, Sentinel staff conducts detailed financial assessment on the individual. The results of that assessment are used to establish a suitable daily fee for the participant—based on their ability to pay—that is accordance with the supervising agency’s approved sliding fee schedule. This no-cost approach for the government can be provided for any of the services we offer.

Through these programs, Sentinel has been able to dramatically reduce the cost of expensive supervision for municipalities and their law enforcement agencies—all while operating with strict adherence to the rules, guidelines and oversight of our customers.

Moreover, our success has been built upon our ability to provide superior value through comprehensive, customizable and scalable services that include hardware, software, local community-based personnel and best-in-class 24/7/365 offender monitoring capabilities.

Robert Contestabile

Founder + Chief Executive Officer

Robert Contestabile has more than 30 years experience in the security and monitoring industry. While serving as President of Florida-based Wackenhut Monitoring Services, Mr. Contestabile purchased the company and Sentinel Offender Services was born in 1993. In the intervening years, Mr. Contestabile has grown Sentinel into one of the largest and most successful electronic monitoring companies in the industry with over 225 customers in 48 states.

In that time, Mr. Contestabile has created an extremely successful track record and has become an undisputed leader in a tumultuous and challenging industry. From the very beginning Mr. Contestabile and his team at Sentinel began building a legacy of innovation—starting with the creation of the first offender-funded monitoring program in the nation. In 1993, Sentinel created the inaugural offender-funded monitoring program that required the participant to pay for all of the fees associated with participating in the program—this truly unique model was the first of its kind. Since its inception, Mr. Contestabile has successfully implemented programs like this across the nation, allowing agencies to operate highly-effective and cost-efficient electronic monitoring programs at no cost to the agency or tax payer.

A key to the successes of these programs has been Sentinel’s 24/7/365 National Monitoring Center, a state-of-the-art electronic monitoring facility located in Irvine, California. Mr. Contestabile created this multi-platform hub to offer national and international customers alike numerous agency- and offender-funded monitoring options that include RF, GPS, alcohol and domestic violence monitoring and prevention. A native of Pennsylvania, Mr. Contestabile earned his Electrical Engineering Degree from the University of Pittsburgh. Since relocating, he enjoys spending the mild winters and beautiful summers that southern California has to offer with his wife Gwen and their wonderful grandchildren. An avid golfer, Mr. Contestabile can often be found taking advantage of any number of California’s fine golf courses.

Darryl Martin

Divisional President + Chief Operating Officer

Darryl Martin has more than 25 years of direct experience within the electronic monitoring industry. His prior experience includes eight years with Digital Products Corporation and nine years at Sentinel Offender Services, where he served as Vice President and General Manager. Mr. Martin transitioned his career to G4S Justice Services in 2007 in order to oversee that company’s nationwide monitoring, technical, and internal operations before becoming its president. As Chief Operating Officer, Mr. Martin maintains executive responsibility for the company’s internal, technical and field operations, which includes the company’s network of field offices that specialize in case and offender management programs that are designed to aid program participants.

Mr. Martin is a graduate of Chapman University and received his MBA from the University of Redlands.

Mark Contestabile

Divisional President + Chief Business Development Officer

Mark Contestabile has worked with Sentinel since 1997. He has worked closely with both Sentinel’s Sales and Operations Team to ensure successful set-up, implementation, and daily program operation across the nation. His extensive training and experience led him to his current position as Chief Business Development Officer/Divisional President, where he provides hands-on leadership and shares his vision for the future direction of the company.

Mr. Contestabile graduated from the Terry College of Business at the University of Georgia.

Sentinel Offender Services - Monitoring Center


Why work for the Monitoring Center?

  • Quality Training programs
  • Hands on experience with monitoring equipment and software
  • Opportunity to develop valuable call center skills
  • Relationship building with law enforcement personnel
  • Growth – Tiered Career Progression Program
  • 24/7 environment, 5, 4 and 3 day work shifts
  • Fun recognition programs

Monitoring Center Qualities

Join the Sentinel family to gain knowledge and leadership qualities, in order to succeed and grow within the company. Sentinel looks for individuals with a thirst for knowledge, employees who utilize their resources and ask questions. Employees are encouraged to incorporate new experiences into their guidebooks and find more ways to efficiently work. As a Sentinel employee your work ethic and display of leadership will be acknowledged.

ISO Certified (International Organization for Standardization)

We are proud to be ISO 9001 certified. Sentinel continually improves and complies with the ISO 9001 Standard to enhance customer satisfaction through effective application of a quality management system.  Our quality management system consistently provides products and services that meet customer applicable statutory and regulatory requirements.

Sentinel Offender Services – Field Operations

Sentinel Offender Services is a pioneer in the offender management space. We establish partnerships with our agency customers to build programs that effectively assist with offender behavior modification and reintegration back into the community to stop the cycle of recidivism. Offender Funded Programs offer a more positive and cost effective alternative to jail. In addition, Agency Based Programs provide Case Management, Electronic Monitoring Services, Moral Reconation Therapy (MRT) instructed classes, Substance and Alcohol Monitoring.

Field Office positions                           

Sentinel provides students and graduates a stepping stone in a Criminal Justice career. The following positions provide face-to-face interaction with probationers, contacts with agency/department personnel and case management training.

Case Manager

The Case Manager provides a service to the contracted Department by handling an assigned caseload of offender’s serving an alternative sentence of electronic monitoring, and is primarily responsible for the comprehensive case management and enforcement of restrictions that are ordered by the Court, Probation, Parole, or Sheriff’s Department.

Administrative Assistant

Provide a professional representation and support to the branch office as needed.

Drug Test Technician

Serve Sentinel customers by collecting offender drug tests through followed procedures and notifying officers of results.

Equipment Installer

Responsible for daily client scheduling, inventory control and installing, removing, as well as, troubleshooting equipment.


Below are locations of our customers we serve:

Los Angeles County Sheriff and Probation Department

San Diego Sheriff and Probation Department

Dallas, TX CSCD

D.C. Pre Trial Services

Connecticut DOC

City of Phoenix, AZ                                            

Butte County, CA Sheriff’s                                                          

Leon County, FL Probation

County of Greenville, SC

Kansas DOC

Riverside, CA Sheriff’s Department

Seattle WA, City of Seattle Municipal Court

Employee Spotlight 

      Sentinel would like to highlight an individual who has shown the progression an employee can achieve at Sentinel Offender Services. We would like to spotlight Paula Guardado.

For over a decade, Paula has risen through the ranks from a Case Manager, to a Branch Manager to her current position. She is responsible for the day to day operations of all of Los Angeles County adult and juvenile programs including the oversight of Sentinel Staff. Los Angeles is a demanding program that requires diligent attention to detail and follow through. Once Paula provided oversight at our Los Angeles location, we have maintained glowing audit reviews from the department.

Paula has been utilized to onboard new employees, train agency personnel and launch new programs throughout the United States. She is always willing to step up and help the organization whenever needed at other, out of state locations. In a few words Paula is DEPENDABLE, PROFESSIONAL and RESPONSIBLE. Thank you Paula!

Sentinel Offender Services Reviews

Rating TrendsRating Trends
Recommend to a friend
Approve of CEO
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Robert Contestabile
28 Ratings
  • "Good company, could use better pay and career advancements"

    • Work/Life Balance
    • Culture & Values
    • Career Opportunities
    • Comp & Benefits
    • Senior Management
    Current Employee - Manager
    Current Employee - Manager
    Neutral Outlook
    No opinion of CEO

    I have been working at Sentinel Offender Services full-time (More than 3 years)


    The staff and people I have worked for and with have all been very respectful and kind. My supervisors all allow me to work on my own with little interference, but are tentative to any needs I have to run my daily operations. Hours are nice (M-F 9-5) type job.


    The pay could be much better. Our counterparts in the probation department make almost double what we do. Advancements seem to be slow, I know people who have been stuck in the same positions for far too long.

    Advice to Management

    Keep up with the "there for you, but do what you are supposed to and we'll leave you alone" method. Bring pay to a more competitive level as people with growing needs are forced to look elsewhere if they need better pay or advancements.

See All 51 Reviews

Sentinel Offender Services Photos

Sentinel Offender Services photo of: Tracking Devices
Sentinel Offender Services photo of: Las Vegas - Day Reporting Center Staff
Sentinel Offender Services photo of: Birthday Celebration
Sentinel Offender Services photo of: Monitoring Center
Sentinel Offender Services photo of: BBQ 2017
Sentinel Offender Services photo of: BBQ 2017
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Sentinel Offender Services Interviews



Getting an Interview

Getting an Interview





    Operator Interview

    Anonymous Interview Candidate in Irvine, CA
    No Offer
    Negative Experience
    Average Interview


    I applied online. I interviewed at Sentinel Offender Services (Irvine, CA) in January 2010.


    Applied on, got a call from a manager and did a phone interview. Got called in to meet in person for another interview. Got the job and obtained a drug test.

    Interview Questions

See All 8 Interviews

Sentinel Offender Services Awards & Accolades

  • Excellence in Employment, Goodwill of Orange County, 2016
  • ISO 9001 Certification, American Systems Registrar, LLC,, 2016

Pledges & Certifications

Veteran Hiring Commitment

Committed to helping America's military veterans find work

Tech Hiring Commitment

Helping to train, hire and promote more technology workers

First Job Programs

Maintain entry-level hiring and career development programs to give people career starts

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