A three-year study in the medical examiner's office in Detroit shows that most cases of SIDS can be attributed to accidental suffocation. The findings are based on a researcher visiting the locations of 209 SIDS-related deaths and asking parents/caregivers to use a doll to demonstrate the positions they left and found the baby in.
Although 23% of cases were initially reported as asphyxiation, position analysis indicated the rate was much higher, around 85%. Babies were typically found face down and/or with their face covered by excessive bedding or a pillow. 53% of cases [111} occurred in an adult bed, and 12%  occurred on sofas.
The Guardian reports that in just over half the cases, adults were sharing the bed or sofa, but it's not clear if that's half bed/sofa cases [e.g., 68] or half the total [e.g. 105]. If it's the latter, then that's over 77% of the co-sleeping cases, which would be a real red flag. However the detailed numbers shake out, though the importance of not putting a kid to sleep face down and of clearing out all soft, smushy, or loose bedding seems pretty clear.
So far, unfortunately, these results aren't yet published. One of the lead researchers, Dr, Melissa Pasquale-Styles, just presented the study Saturday morning at the Kids Pathology session of the American Academy of Forensic Sciences annual meeting in Seattle. The paper was titled, "Infant Position and the Assessment of Risk Factors for Asphyxia: A Review of 209 Sudden Unexpected Infant Deaths."
Other talks more likely to come soon to a CSI episode near you: "Is Your Daughter Trolling for Pedophiles On The Internet?", "Death by Radio-Controlled Helicopter," and of course, "Killer Hairdryer," which has already been optioned by Paramount.
Most cot deaths due to accidental suffocation, says US study [guardian]
AAFS 2006: "See you in Seattle!" [aafs.org]
Previously: Coming out of the co-sleeping closet
Other SIDS-related posts, including the JPMA's work for the all-powerful crib bumper lobby