  Millilensed gravitational waves (GWs) can potentially be identified by the
interference signatures caused by $\sim\!O(10\textrm{--}100)~\textrm{ms}$ time
delays between multiple overlapping lensed signals. However, distinguishing
millilensed GWs from GWs generated by precessing binary black-hole mergers can
be challenging due to their apparent similar waveform shapes. This
morphological similarity may be an obstacle to template-based searches to
correctly identifying the origin of observed GWs and poses a fundamental
question, can we discern millilensed GW signals from signals produced by
precessing binary black holes? In this study, we investigate the feasibility of
distinguishing between these GWs by performing a proof-of-principle injection
study of simulated millilensed precessing GW signals, within the context of
ground-based LIGO-Virgo-KAGRA detector network detections. Our findings
indicate that it is possible to differentiate between the two effects by
comparing signal-to-noise ratios (SNRs) computed using templates based on
different hypotheses for the target signal. We further show from the parameter
estimation study that while lensing magnification is sensitive to precession,
it is possible to identify millilensing in precessing GW signals with an SNR of
18. The recovery of precession in the presence of lensing is more challenging
but improves significantly for signals with an SNR of 40. Nonetheless,
neglecting millilensing effects results in biases in the recovered spins,
revealing the importance of accounting for these effects in accurate GW signal
analysis.
