The first murder of the year happened just a few hours into 2020, when Isaiah Usen-Satchell was stabbed to death close to his home in Norfolk Park.
Two men have been charged over his death.
Just a week later, two-year-old Keigan O’Brien died in Doncaster after being admitted to hospital in cardiac arrest.
A post mortem examination revealed the toddler had suffered head injuries.
His mum Sarah O’Brien, 32, and her boyfriend Martin Currie, 36, have been charged with murder.
The most recent death to trigger a murder probe was that of 39-year-old Leighton Owen, who was found dead in a flat in Hatfield House, Grove Place, Balby, Doncaster, shortly after 11pm on Wednesday, August 26.
Two women, aged 45 and 40, and a 21-year-old man, were arrested on suspicion of murder and later released under investigation as enquiries continue.
Anyone with information about any of the deaths should call South Yorkshire Police on 101 or Crimestoppers on 0800 555111.
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5. 5) Stabbing
A 31-year-old woman was stabbed in a Barnsley street on March 29. A 40-year-old man charged with murder is due to stand trial later this month. Photo: Claire Lewis
6. 6) Assault
Stafford Garner, 46, was found by paramedics injured at his home in Monsal Street, Thurnscoe on April 2, and died in hospital three days later. A number of arrests have been made but nobody has been charged. Photo: Claire Lewis
7. 7) Unascertained
Terry Johnson, 49, died at a flat in Gell Street, Broomhall, on May 15. A 51-year-old man was arrested suspicion of murder and a 47-year-old man was arrested on suspicion of supplying a controlled drug. Both were released under investigation. Photo: Claire Lewis
8. 8) Assault
Paul Crossley, 53, died on May 19 - four days after suffering a head injury during an altercation between a group of men on Longley Hall Way, Longley, Sheffield. Sean Holt, 43, of and Richard Ferrie, 44, both of Longley Hall Way, have been charged with murder. Photo: Claire Lewis