Newsday undertook an extensive, four-month review of reporting by Kevin Deutsch, who covered law enforcement from April 2012 to September 2016.

The review of the former Newsday reporter’s work began after The Baltimore Sun this year reported that law enforcement and other officials questioned the veracity of Deutsch’s nonfiction book “Pill City” about Baltimore’s drug trade. In addition, questions arose about individuals named in Newsday stories by Deutsch. Book publisher St. Martin’s Press and Deutsch have said they stand behind the book.

We are dedicated to accurate, factual reporting, to the highest journalistic standards and to maintaining our credibility with Newsday readers. We also are committed to being accountable to our readers. Newsday undertook the detailed review in that spirit and because of the concerns that were raised.

In late February, as our review was under way, The New York Times reported in an editor’s note that The Times “had been unable to locate or confirm the existence of two people who were named and quoted” in a Dec. 29, 2016, freelance article written by Deutsch. Deutsch “maintains that the interviews and the descriptions are accurate,” The Times wrote.

Newsday reviewed 600 stories with reporting by Deutsch. We contacted officials in the police departments regularly involved in Deutsch’s coverage. They said they had not had problems with his work. We then focused our research and reporting on individuals who, as described in the stories, would not be considered officials, or well-known, public figures.

The review found 77 stories with 109 individuals from Deutsch’s reporting whom Newsday could not locate. The main points of the stories were not affected. While two stories about the Orlando nightclub shooter Omar Mateen were based on sources Newsday could not locate, other media reported the main points of those stories but with attribution from different sources. Newsday is attaching an editor’s note to each story online that contains individuals we cannot locate.

Here’s how Newsday conducted the review:

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Researchers and reporters searched local and national public records, sites providing nationwide people searches, databases of business, real estate and conviction records, social media sites including Facebook, LinkedIn and Ancestry.com and nationwide news archives. They searched potential alternate spellings and other name variations. Their reporting followed potential leads they found through research, within stories and in information shared by Deutsch during the review.

Finding people after publication, in some cases years later, can be difficult because of changes in residence, circumstance and contact information. Some may not have given their real names.

On the law enforcement beat, reporters may encounter people who lead lives that are not reflected in public records or other sources of information that would help locate them. It is possible that some on our list were difficult to find or reluctant to respond to our review because they are undocumented immigrants, those battling or recovering from addiction or people involved in or around illegal activity.

Some on our list were described discussing crimes in their neighborhoods, and others as relatives, friends or neighbors of victims or as individuals living near or knowing those accused of crimes.

Others we have not been able to locate, though, are described as bystanders, neighbors, spectators, relatives of drug victims, witnesses to news events or related in some way to people in the news. Still others are described in stories as people actively engaged in public issues, such as activists, protesters and marchers. Many individuals on the list are described as local.

Deutsch said in email exchanges with Newsday that “I have no doubt about the veracity of the claims of the sources I quoted.” He also said, “Not a single public official, source, or other interviewee has raised any issues with even one of these stories.”

“It’s impossible for any reporter to know whether the name given to him by interviewees on the street — or those reached briefly by phone or email — is that person’s full and legal name, rather than an alias or variation of their real name (maiden names and certain common nicknames/abbreviations for first names are often published by newspapers, including Newsday.). But every one of the names on Newsday’s list was the name given to me by that interview subject, verbatim.”

During the four months of our review, Newsday shared questions and updates with Deutsch as we progressed in the search for individuals we could not locate. We requested notes and contact information. Deutsch sent us notes he said represented all individuals we were unable to locate and responded over the course of the review by email, sharing information he said was from his recollection and notes.

Reporters followed up on all information shared by Deutsch. He did not provide contact information for those on our list. Newsday reporters and editors sought unsuccessfully several times to meet with Deutsch to discuss his reporting and to review his notes together to ensure we were not missing contact information or other details that might help locate individuals. Deutsch maintained that the notes he shared “serve as evidence of interviews” with each source.

Deutsch said he kept contact information in a Rolodex he left behind at Newsday’s main office and in a company-issued cellphone he returned within a week after resigning on Sept. 6, 2016. Editorial staff did not find a Rolodex or other notes at our office, but found notes left at Newsday’s desk at a courthouse pressroom where he worked. We shared them with Deutsch and he confirmed they were his. As per company policy, the contents of the cellphone had been deleted immediately after Deutsch returned it to Newsday.

Maintaining the trust of our readers is essential to our mission. If we are able subsequently to locate any individuals, we will update our stories.