The 16-year-old labourer was photographed at Dubbo Gaol in January 1893 while awaiting trial for the murder of Jessie Hammling outside her home.

Evidence presented at Mr Astill's trial suggested ambiguities existed in his account of the woman's death.

He claimed it had resulted from the accidental firing of a shotgun he held when he tripped over Ms Hamming's pet kangaroo.

The judge summed up for Mr Astill's acquittal and the jury found him not guilty.

After marrying in 1901 and fathering a large family, Mr Astill died in Narromine in 1965.

Mr Astill's story will be told as part of Captured: Portraits of Crime, 1870-1930, which explores the fates of men, women and children incarcerated in NSW gaols.

NSW State Archives Senior Advisor Wendy Gallagher will speak at the official opening of Captured at 5.30pm on Wednesday.

Ms Gallagher said the portraits of prisoners and associated documents preserved in the archives collection were "powerfully engaging".

"The stories of people caught up in a NSW justice system of much earlier times give us a remarkable glimpse of what life was like for many and how harsh and desperate it could be," she said.

"Every portrait has its own unique tale to tell."

The exhibition features information and images sourced from 46,000 inmate records contained in 199 gaol photographic description books.

The records have been digitised to preserve history and protect the information for future generations.

"Our experts have peeled back the layers of these historical records and illuminated the events that led these people to commit a crime," Ms Gallagher said.

"We looked at the offence type, gender, age and location of crimes to piece together a collection of compelling stories for the exhibition and catalogue."

Among those featured in the month-long exhibition is the story of Sarah Clifford, a former convict and known pickpocket in NSW.

She was photographed numerous times between 1872 and 1910 in Darlinghurst and Biloela gaols where she was incarcerated.

Her last known conviction was in 1910 when she was sentenced to six months light labour.

Her prison sentences, when added together, total over 36 years.

The full story of Mr Astill's trial can be heard on the State Archives website.