I am so saddened to hear of the passing of Prof. Lillis. At the beginning of my graduate school journey through the CS Department at UIC, I took Algorithms with him, a daunting subject from my undergraduate days. Dr. Lillis was extremely kind and generous with his time helping me figure out how to prove how fast an algorithm could run. He was a gifted teacher. His lectures were thorough and coherent, and he drew the best from his students. 

I owe him a lot, and I am not alone.

May you all find peace and joy in his memory.

With warmest regards,
David Randolph

I am so saddened to hear about the passing of Professor Lillis. I was a student at UIC from 1998-2001 and he taught me EECS 360 (Algorithms and Data Structures) He was also my advisor for the Senior project. Hands down, he was the best teacher I had and played a huge part in my success as a programmer.  He touched many lives with his patience and kindness. This picture is from my graduation in summer of 2001. My heartfelt condolences to his family and loved ones.

I've attached a memory I found from 2017, back when I was attending UIC, that reflects the deep appreciation so many of us had for Professor Lillis.

I'm heartbroken to hear of his passing. As a UIC alumnus from the Computer Science program, I’ll always be grateful for the impact he had on my education and my life. Professor Lillis had a remarkable way of teaching. His lessons truly resonated and inspired me to keep going when things were difficult. I took every opportunity to learn from him, because his classes were more than just lectures, they were experiences filled with honesty, insight, and encouragement to learn.

He was an open book, always willing to share knowledge and guidance far beyond the classroom. His generosity of spirit and dedication to his students left a lasting mark on everyone who had the privilege of learning from him.

My deepest condolences go out to his family and loved ones. May they find comfort in knowing how profoundly he touched the lives of his students and how fondly he will be remembered.

I remember Professor Lillis's care in teaching and his want to help people learn the how and why in his courses.

I was a TA and peer tutor for Lillis. He taught in C and wanted us to code in terminal to understanding and appreciate computers. Students told me they felt more confident in themselves and belonging in engineering after taking Lillis's classes. Some came in with their own weights and Professor Lillis had an impact that not only helped them learn, but overcome their doubts. I’ve recalled his lessons over the years as the best way to learn and reach people.

Heartfelt condolences to Rebecca and Maggie. And a few words on John: I remember him as a gentle, thoughtful colleague who never raised his voice, was always to the point and was able to help clarify any issues or concerns that had been brought up at meetings or in informal conversations.
And we owe him and Rebecca, because when in 2000 we were living in Lincoln Park and looking to buy a house, and not sure where, we ended up going out for dinner with them: they gave us their unvarnished opinion about living in Oak Park, mostly the good and the occasional bad. And here we have been for 25 years.
So here's to the memory of a gentle soul. Peace be with him, and with his family navigating the world without him.

I was deeply saddened to hear of John’s passing. I had the privilege of knowing John during our time together in Professor Cheng’s lab at UCSD. Though many years have passed, I still remember his sharp mind, his humility, and his warm presence in the lab. John will be remembered not only for his talent and academic accomplishments as a professor, but also for the genuine and kind person he was. He will be greatly missed.

Rest in peace, John.

John was a wonderful friend and he will be dearly missed.

Rest in peace, John. You will be greatly missed. 

-- Bhaskar

Dear Lillis Family:

I heard this sad news from Professor Chung-Kuan Cheng, the PhD advisor of John. I feel really, really sorry about his passing. Although I have not met John before, but I have heard many people talking about his contribution to the EDA society, where all his findings and works are still inspiring the current researchers. My big condolences to your family. May he rest in peace in heaven.

Yours Sincerely,
Jingwei Lu

I still remember the scene when I attended Rebecca and John's wedding at Old Town, San Diego. It was a beautiful day. The place was serene, and the ceremony was simple and elegant.
I was glad when the couple adopted Maggie for a bigger family. I then got a picture of Maggie for every Christmas to see how she grew up year by year.
Time flies so fast. I feel sad that we lost a great researcher and educator with passion and action for teaching. Nowadays, I will refer to our coauthored book: Interconnect Analysis and Synthesis, which has been translated into Chinese and Japanese publications. John's paper on wire sizing and buffer insertion remains highly cited. His Mongrel placement provides a new angle to tackle physical layout problems. -CK Cheng, UC San Diego

I was deeply saddened to hear about the passing of Professor John Lillis. It is difficult to put into words the immense impact he had on my life, both as a student and as a person. I had the great privilege of being one of his students at UIC, and during some of my most uncertain and challenging moments in college, he was the one who guided me back onto a path of clarity and purpose.

Professor Lillis possessed a rare combination of brilliance, patience, and genuine care for his students. His intellect was undeniable—his lectures were always thought-provoking, and his homework assignments, though daunting at times, pushed us to grow far beyond what we believed we were capable of. I still vividly remember struggling through his challenging problem sets, some of which kept me awake late into the night. To this day, I can honestly say that I still have nightmares about NP-complete problems, yet I would not trade those experiences for anything, because they taught me resilience, persistence, and a deeper appreciation for the beauty of computer science.

Beyond his unmatched academic rigor, what stood out most about Professor Lillis was his generosity of spirit. He gave me the opportunity to conduct research under his guidance, and he supported me not only in my academic pursuits but also in matters of life beyond school. He took the time to mentor me, to offer advice, and to encourage me to see possibilities when I felt lost. His belief in me was transformative, and I know that I would not be who I am today without his influence.

Professor Lillis was more than just a teacher; he was a mentor, a guide, and an inspiration. His legacy will live on in the countless students he taught, challenged, and inspired. Though his loss is deeply felt, I will carry his lessons and his kindness with me for the rest of my life. My sincerest condolences go out to his family, friends, colleagues, and all who were fortunate enough to have known him.

May his memory be a blessing. I never knew him, but everyone I know speaks highly of him.

It still feels like yesterday seeing John walk into Professor CK's lab—always generous, kind, intelligent, and deeply passionate about his PhD research. Back in 1994–1995, thirty years ago, it was a special period of life shared with John—we were all so young, and he stood out not only as one of the most dedicated and capable scholars in CK's lab but also as someone destined to become a remarkable educator and scientist. I still remember him as one of the smartest, calmest, and most intellectual PhD students in the lab, with a thoughtful presence and quiet determination. For me, John will always remain in my memory as the same charming, handsome, and inspiring person, forever.

It is a tremendous loss that John, a well-acknowledged professor who made such an impact in research and teaching, has passed away at the young age of 58. My heartfelt prayers go with him—may he rest in peace. I hold his family in my thoughts during this difficult time. His contributions will continue to inspire and guide future generations of researchers and students.

With deepest sympathy,
Yaxin

I had the privilege of being John's colleague since the time he joined UIC in 1997. I served as department head of computer science during the early part of John’s career and later as dean of engineering. 

John played a pivotal role in the development of UIC’s CS department which was started in 2001 and is now the largest department at UIC.  John was always very unselfish with his time and was always willing to help out in many different areas in addition to his core faculty duties of teaching and research. John was an exceptional colleague and a wonderful human being.  He showed our students kindness, care and concern and he will be deeply missed.

My condolences to his family and many friends.

Sincerely,
Pete Nelson

I worked with John as a fellow faculty member in the CS department at UIC. John was extremely pleasant to work with. It was a joy to know and work with him for more than twenty years. 

My deep and heart felt condolences to Rebecca and Maggie. May John's Soul rest in peace.

Prasad Sistla

My deepest condolences. I had the privilege of being one of Professor Lillis’ students at UIC, and he was by far my favorite professor. His compassion and dedication to making sure everything clicked for me have stayed with me long after graduation. That impact went beyond academics and reflected the kind of person he was.

Professor Lillis cared deeply for everyone around him, both inside and outside the classroom. I went to him not only for help with class but also for conversation, advice, or simply to ramble, and he never made me feel like I was a burden. Instead, he listened, and that gift was invaluable to me. He wasn’t a man of many words, but the ones he shared have stayed with me and I am thankful that I the opportunity to know him.

Rest in peace, Professor Lillis.

I am really shock and deeply sadden to hear the news of John's passing. I had about two years of overlapping with John when I worked as post-doctor under the supervision of Prof. CK Cheng in UC San Diego. I still have fresh memory of his smiling,  kindness, spirit and eager to help. John and I had a couple of co-authored papers and I still remember we worked late in lab in order to submit in the last minutes. 
May John rest in peace, and please accept my sincere condolence,

John and I shared advisors who lead groundbreaking research at the height of the circuit and systems era: Professors T. Y. Lin and C. K. Cheng. John was the algorithm voice in group discussions amongst us engineering students. He provided valuable insights and inspired his peers to think creatively. It is a devastating loss that John left us so soon. His work will forever be a beacon for our fields of study. Sending my deepest condolences in celebrating John's life.

I am deeply saddened to hear of John's passing.  On a professional level, I worked with him for over two decades at UIC.  I recall his big contribution to the CS Department serving as the Director of Undergraduate Studies for many years.  In that capacity, he helped me set up courses in mobile app development and software engineering.  On a personal level, he was a fellow Oak Park resident; I loved to hear stories about Maggie, whom he loved so deeply.  He was a devoted husband to Rebecca and father to Maggie.    Please accept my most heartfelt condolences.

John was a Loving Husband to Becky , Devoted and Caring Father to
Maggie, a Loyal Friend and we are Honored to call him our Nephew.
If you were Lucky enough to know John, as the Irish say, you are
lucky enough. Rest in Peace Sweet, John, you are forever in our Hearts and Prayers .
Uncle Denny and Aunt Nancy

I am so thankful for the good times and things we both had in common. I’ll always remember having our fantasy football consults before each season started and how much you helped me with picking out my first motorcycle. Every time I ride, I feel closer to you.

OBITUARY

John Patrick Lillis

19 August, 1967 – 7 September, 2025

Remmert Funeral Home

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