Sir Henry Duncan Littlejohn MD LLD FRCSE (8 May 1826 – 30 September 1914) was a Scottish surgeon, forensic scientist and public health official.

This was at a time when many of the town's inhabitants were living in squalor, in filthy overcrowded tenements, often with no water supply and with little or no sanitation.

[5][4] During his first three years in the post, Littlejohn carried out a meticulous investigation into the living conditions and the state of health of the town's inhabitants.

His report, published in 1865, contained 120 pages of detailed statistics, analysing conditions in over one thousand separate streets, closes and tenements.

[6] With the backing of Littlejohn's report, the Lord Provost, William Chambers, and the Town Council launched an ambitious programme of urban renewal in Edinburgh.

This resulted in the demolition of the worst slums and created the largely Victorian Old Town that exists today.

On Littlejohn's recommendation, the council also brought in regulations governing water supply, sewage, building standards, food hygiene, waste disposal and the management of cemeteries.

Despite opposition from doctors, a clause was added to the 1879 Edinburgh Municipal Police Act making such notification compulsory – the first legislation of its kind in Britain.

[9] His introduction of compulsory notification of infectious diseases has been described as 'one of the major advances in public health of the 19th century'.

He went on to serve as medical adviser to the Crown in Scottish criminal cases, in which role he would continue for over 50 years.

[2][3] At the time of his retirement in 1908, the Scotsman noted that "there was no great criminal trial in the High Court in which he did not act as a Crown witness.

[2] His son was Henry Harvey Littlejohn (1862–1927) (normally just called Harvey Littlejohn during his life but posthumously largely called Henry) who followed in his father's footsteps as a forensic scientist and medical officer, and who adopted similar techniques of investigation and problem solving.