“Jacko” Jackson: detective inspector of the East Midlands Combined Constabulary, in Leicester, England, by Frank Palmer

Paul Jacobson: 80-something amateur sleuth, in the Geezer-Lit series by Mike Befeler

Daniel Jacobus: blind, reclusive, and crotchety violin teacher living in self-imposed exile in rural New England, by Gerald Elias

Herman Jackson: bail bondsman and former Detroit bookie, in St. Paul, Minnesota, by Richard A. Thompson

Jefferson “J. W.” Jackson: 30-something ex-Boston cop, in Martha’s Vineyard, Massachusetts, by Philip Craig

Jill Jackson: police detective sergeant, and childhood rape victim, in Sydney, New South Wales, Australia, by Leah Giarratano

Jolene Jackson: free-lance journalist, whose trouble starts whenever she goes home to Kickapoo, Texas, by Paula Boyd

Kane Jackson: industrial espionage expert and detective, by William Arden (Dennis Lynds)

Taylor Jackson: homicide lieutenant, and her lover, FBI profiler John Baldwin, in Nashville, Tennessee, by J.T. Ellison

Wade Jackson: homicide detective in Eugene, Oregon, by L.J. Sellers

William “Tough” Jackson and Ed Razoni, cops in New York City, by Warren Murphy

Matt Jacob: former social worker, now a private investigator with a drug problem, in Boston, Massachussets, by Zachary Klein

Calista Jacobs: illustrator of children’s books in Cambridge, Massachusetts, by Kathryn Lasky Knight

Frank Jacobsen: detective chief inspector, and detective sergeant Ian Kerr, in Crowby, in the Midlands of England, by Iain McDowall

Miles Jacoby: boxer turned private investigator in New York City, by Robert J. Randisi

Milan Jacovich: blue-collar Slovenian private eye with a master’s degree in Cleveland, Ohio, by Les Roberts

Daniel Jacquot: former rugby player, now a homicide chief inspector, in Marseilles, France, by Martin O’Brien

Jo Jacuzzo: charismatic lesbian in Buffalo, New York, by Anne Seale

Amanda Jaffe: attorney in Portland, Oregon, by Philip Margolin

Simon Jaffe, known as “Red Diamond”, a taxi-driver, pulp fiction collector, and private investigator, in New York City, Los Angeles, and Las Vegas, by Mark Schorr

Michael Jagger: swaggering British spy, by William Garner

Cassidy James: lesbian private investigator in the fictional town of Cedar Hills (near the Southern Oregon Coast about 350 miles from Portland), by Kate Calloway

Cassandra James: professor and administrator at St. Etheldreda’s College, in Cambridge, England, in the Cambridge mysteries by Christine Poulson

Dewey James: 60-something small town librarian in Hamilton, Kentucky, by Kate Morgan

Evelyn James: forensic expert in the medical examiner’s office, in Cleveland, Ohio, by Elizabeth Becka

Gemma James: Scotland Yard sergeant, Duncan Kincaid, a superintendent, in London, England, by Deborah Crombie

Harry James: detective sergeant, later inspector at Scotland Yard, based in London, England, by Kenneth Giles

Jessica “Jesse” James: investigative reporter in Rochester, New York, by Meg O’Brien

Lis James: journalist turned public relations officer for a mental health center, in Houston, Texas, by Karen Hanson Stuyck

Mira James: assistant librarian and part-time reporter, in Battle Lake, Minnesota, in the Murder-by-Month mysteries, by Jess Lourey

Cass Jameson: criminal lawyer in Brooklyn, New York, by Carolyn Wheat

Lucky Jamieson, inheriting the By the Spoonful Soup Shop, in fictional Snowflake, Vermont, in the Soup Lover’s mysteries by Connie Archer

J.J. Jamison: computer engineer and investigator with CATCH (Committee for Analysis of Tropospheric and Celestial Happenings), in Minneapolis, Minnesota, by L.A. Taylor

Frank Janek: NYPD homicide detective in New York City, by William Bayer

Cliff Janeway: cop and rare book expert, in Denver, Colorado, by John Dunning

Willa Jansson: law student, then lawyer, and a child of idealistic, left-wing parents, in San Francisco, California, by Lisa Matera

Ben January: surgeon and music teacher, in 1830s New Orleans, Louisiana, by Barbara Hambly

David Jardine: spymaster with the British Secret Intelligence Service, on assignment around the world, by Murray Smith

Oliver Jardine: police detective, and Theresa Fortunato, tarot-reading psychic, in Los Angeles, California, by Kate Green

Rev. Jabal Jarrett: eccentric Anglican vicar in and near Auckland, New Zealand, by Freda Bream

Elena Jarvis: wise-cracking police detective, in Los Santos, Texas, by Nancy Herndon (Nancy Fairbanks)

Jarrod Jarvis: former child-star and gay amateur sleuth, in Los Angeles, California, and London, England, by Rick Copp

Jazz Jasper: American safari guide in Kenya, by Karin McQuillan

Kate Jasper: vegetarian and gag-gift wholesaler, in Marin County, California, by Jaqueline Girdner

Earl Jazine and Carl Crader, computer cops in the future, by Edward D. Hoch

Tal Jefferson: defeated attorney who escapes the big city and returns to Wynnton, South Carolina, the small town where she was raised, by Tracy Dunham

Mrs. Jeffries: housekeeper for Inspector Witherspoon, a policeman in London, England, in the Victorian mysteries by Emily Brightwell

Harriet Jeffries: photographer, and John Sanders, a police detective, in Toronto, Ontario, Canada, by Medora Sale (Caroline Roe)

Jane Jeffry: suburban housewife and sleuth in Chicago, Illinois, by Jill Churchill

Domenic Jejeune: a Canadian police officer newly installed as Detective Chief Inspector in the town of Saltmarsh, Norfolk, England, in the Birder Murder mysteries by Steve Burrows

Miss Jenkins, a “Gal Friday”, and Jake Rossiter, a private investigator, in post-World War II Seattle, Washington, by Curt Colbert

Elise Jenkins: reporter for the Ocean Point Weekly, and Mitch Burns, a police detective, in Ocean Point, New Jersey, by Laura Bradford

Glyndwr Jenkins: and David Brade, police detectives in Cardiff, Wales, by David Craig (Bill James)

Harry Jenkins: lawyer in a small wills and estates firm in Toronto, Ontario, Canada, in the Osgoode Trilogy, by Mary E. Martin 

Matthew Jenkyn: 15th century soldier and double agent spy, in England, by P.C. Doherty

Dr. Edward Jenner: forensic pathologist who quit his job in Manhattan after 9/11, later a medical examiner in fictional Port Fontaine, Florida, by Jonathan Hayes

Jimmy Jenner: pensioned-off cop with a wooden leg in the Stoke Newington section of London, England, by John Milne

Harper Jennings: Iraq war veteran with PTSD, now a teaching assistant at Cornell University, in New York, by Merry Jones

Sergeant Alex Jensen: state trooper, and Jessie Arnold, a dog sled racer, in Anchorage, Alaska, by Sue Henry

Georgia Jensen: historical researcher turn sleuth, by P.A. Stelzer

Ophelia Jensen: reluctant witch who is a librarian, and her grandmother Abby, in a small town in Iowa, by Shirley Damsgaard

Troy Jensen: operative for Red Cell Seven, a highly classified intelligence agency tasked with protecting America from the most catastrophic of terrorist attacks, by Stephen Frey

Martin Jerrold: lieutenant in the British Navy in the early 1800s, in the Reluctant Adventures trilogy, by Edwin Thomas

John Jericho: artist and crusader, by Hugh Pentecost (Judson Philips)

Jesus Creek: an eccentric small town in Tennessee, by Deborah Adams

Jethro: cat burglar recruited by MI5, in post-WWII London, England, by Tony Broadbent

Rita Jewel, selling clothes and accessories to socialites at Dolce's Boutique, in San Francisco, California, in the Accessories mysteries by Grace Carroll (Carol Culver)

Sonchai Jitpleecheep: police detective in Bangkok, Thailand, by John Burdett

Sister Joan: investigative nun in Cornwall, England, by Veronica Black

Natalie Joday: investigative reporter in Bergen County, New Jersey, by Ellen Larson

Kimmo Joentaa: police detective in Turku, Finland, whose wife recently died from Hodgkin’s disease, by Jan Costin Wagner

Bruno Johnson: former Los Angeles County Deputy Sheriff and ex-con, by David Putnam

Gertie Johnson: 60-something sleuth in the Upper Peninsula of Michigan, in the Yooper mysteries by Deb Baker

Hilda Johansson: young immigrant from Sweden working as a servant for the Studebaker family around the turn-of-the-19th century in South Bend, Indiana, by Jeanne M. Dams

John the Eunuch: Lord Chamberlain to the Emperor Justinian in Constantinople in 537, by Mary Reed and Eric Mayer

Coffin Ed Johnson and Grave Digger Jones, detectives in Harlem, living in Astoria, Queens, New York, by Chester Himes

Frank Johnson: private investigator in Virginia and then West Virginia, by Ed Lynskey

Johnson Johnson: British agent and yachtsman on the “Dolly” by Dorothy Dunnett

Dr. Sam. Johnson: real-life 18th-century lexicographer and sage, in London, England, by Lillian De La Torre

Samuel Johnson, his dachshund Boswell, and an unlucky demon named Nurd, in an adult fantasy thriller series for children by John Connolly

Mr. Jones: bodyguard and private investigator, and Carly Wagner, a Texas congresswoman, in Washington DC, by Jo-Ann Power

Abel Jones: federal agent during the American Civil War, by Owen Parry

Callie Valentine Jones: a hairdresser at her Uncle Charlie’s mortuary, Elvis Presley, reincarnated as a basset hound, and Lovie, a caterer, near Tupelo, Mississippi, in the Southern Cousins mysteries by Peggy Webb

Casey Jones: unlicensed private eye in North Carolina, by Katy Munger

Casey Jones: cruise director on the luxury cruise ship Countess Georgina, in the Caribbean and the Mediterranean, by Stella Whitelaw

Cleopatra Jones: special agent fighting drug trafficking, by Ron Goulart

Cleopatra Jones: accountant, golfer, and divorced mother of two, in Hogan’s Glen, Maryland, by Maggie Toussaint

Demary Jones: owner of Confidential Research, specializing in genealogy and historical research, in Seattle, Washington, by E.L. Larken

Fremont Jones: owner of a typewriter service in turn-of-the-19th-century San Francisco, California, by Dianne Day

Grave Digger Jones and Coffin Ed Johnson, detectives in Harlem, living in Astoria, Queens, New York, by Chester Himes

Hannibal Jones: in Washington, DC, by Austin S. Camacho

Jupiter Jones: Harvard fine arts instructor and amateur sleuth, in Boston, Massachusetts, by Timothy Fuller

Kelly Jones: FBI agent in New England, by Michelle Gagnon

Lavender (Snake) Jones, a zookeeper, and her husband Jeff, an Aussie herpetologist, in Minnesota, by Marilyn Victor & Michael Allan Mallory

Lena Jones: of Desert Investigations in Scottsdale, Arizona, by Betty Webb

Olivia Taylor Jones, from a prominent Chicago family, finds out she’s the adopted daughter of notorious serial killers, in Cainsville, Illinois, in the Cainsville trilogy by Kelley Armstrong

Ridley Jones: freelance writer in New York City, by Lisa Unger (Lisa Miscione)

Sam Jones: sculptor in Camden Town, London, England, by Lauren Henderson

Tallulah “Tally” Jones: recently divorced and running an ice cream shop (Remember the A La Mode) in Dalliance, Texas, in the Mystery a la Mode series by Wendy Lyn Watson

Texana Jones: trading post owner in the Big Bend Region of Texas, by Allana Martin

Tom Jones: health investigator for the Home Office, and sometimes Jo Farewell, a nursing sister at Latchvale Hospital, in England, by Andrew Puckett

Tyler Jones: lesbian feminist newspaper columnist, based in San Francisco, California, by Joan M. Drury

Magnus Jonson: born in Iceland, raised in Boston, back working as a homicide detective in Iceland, in the Fire and Ice series by Michael Ridpath

Scott Joplin, in the Ragtime series by Larry Karp

Casey Jordan: criminal defense attorney in Dallas, Texas, by Tim Green

John Jordan: prison chaplain at the Potter Correctional Institution in north Florida, by Michael Lister

Raisa Jordan: agent for the US Diplomatic Security Service assigned to Tel Aviv, Isreal, by Chris Goff

Scott Jordan: brash young lawyer in New York City, by Harold Q. Masur

Trevor Joseph: a depressed police sergeant, later inspector, of the Serious Crimes Squad, in medical thrillers set in England and Wales, by Katherine John

Miss Julia: elderly widow in Abbotsford, North Carolina, by Ann B. Ross

Jimm Juree: former crime reporter for the Chiang Mai Daily Mail, now living with her family in rural southern Thailand, by Colin Cotterill

Ben Jurnet: detective inspector, raised a Unitarian, perhaps of Jewish descent, in Norfolk, England, by S.T. Haymon

Richard Jury: Scotland Yard investigator based in London, England, by Martha Grimes

Benjamin Justice: reporter in Los Angeles, California, by John Morgan Wilson

Charlotte Justice: black homicide detective in Los Angeles, California, by Paula L. Woods

Stacy Justice: 20-something reluctant witch working as a reporter, and her Great Dane Thor, in fictional Amethyst, Illinois, by Barbra Annino

Henning Juul: veteran investigative crime reporter, in Oslo, Norway, by Thomas Enger