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Being one of only two fundamental properties black holes possess, the spin ofsupermassive black holes (SMBHs) is of great interest for understandingaccretion processes and galaxy evolution. However, in these early days of spinmeasurements, consistency and reproducibility of spin constraints have been achallenge. Here we focus on X-ray spectral modelling of active galactic nuclei(AGN), examining how well we can truly return known reflection parameters suchas spin under standard conditions. We have created and fit over 4000 simulatedSeyfert 1 spectra each with 375$\pm$1k counts. We assess the fits withreflection fraction of $R$ = 1 as well as reflection-dominated AGN with $R$ =5. We also examine the consequence of permitting fits to search for retrogradespin. In general, we discover that most parameters are over-estimated whenspectroscopy is restricted to the 2.5 - 10.0 keV regime and that models areinsensitive to inner emissivity index and ionization. When the bandpass isextended out to 70keV, parameters are more accurately estimated. Repeating theprocess for $R$ = 5 reduces our ability to measure photon index ($\sim$3 to 8per cent error and overestimated), but increases precision in all otherparameters -- most notably ionization, which becomes better constrained($\pm$45 erg cm $\rm{s^{-1}}$) for low ionization parameters ($\xi$$<$200 ergcm $\rm{s^{-1}}$). In all cases, we find the spin parameter is only wellmeasured for the most rapidly rotating supermassive black holes (i.e. $a$ $>$0.8 to about $\pm$0.10) and that inner emissivity index is never wellconstrained. Allowing our model to search for retrograde spin did not improvethe results.

How well can we measure supermassive black hole spin?