University of Bristol - Historical Photographs of China reference number: Os04-019. Photo from an album (UoB reference Os04) kept in the School of Oriental and African Studies Archives, London (SOAS reference MS 380 876/4).
This photo is reproduced in Clark Worswick 'Imperial China', page 63, with the caption: 'Attributed to W. Saunders: Execution Scene, Shanghai, 1870s.'
Also reproduced in L. Carrington Goodrich and Nigel Cameron 'The Face of China 1860-1912' with the caption: 'Photographer unknown: Execution scene, c1860'.
Perhaps this is a scene set up by the photographer, to illustrate an execution, using models?
Photograph by William Thomas Saunders (1832-1892).