diff --git a/policy/policy.go b/policy/policy.go
index 908aefab..5ab2408e 100644
--- a/policy/policy.go
+++ b/policy/policy.go
@@ -239,30 +239,30 @@ func (p Policy) Verify(ctx context.Context, opts ...VerifyOption) (bool, map[str
 	resultsByStep := make(map[string]StepResult)
 	for depth := 0; depth < vo.searchDepth; depth++ {
 		for stepName, step := range p.Steps {
-			// initialize the result for this step if it hasn't been already
-			if _, ok := resultsByStep[stepName]; !ok {
-				resultsByStep[stepName] = StepResult{Step: stepName}
-			}
-
+			// Use search to get all the attestations that match the supplied step name and subjects
 			collections, err := vo.verifiedSource.Search(ctx, stepName, vo.subjectDigests, attestationsByStep[stepName])
 			if err != nil {
 				return false, nil, err
 			}
 
 			if len(collections) == 0 {
-				continue
+				collections = append(collections, source.CollectionVerificationResult{Errors: []error{ErrNoCollections{Step: stepName}}})
 			}
 
-			// Verify the functionaries and validate attestations
+			// Verify the functionaries
 			collections = step.checkFunctionaries(collections, trustBundles)
-			stepResult := step.validateAttestations(collections)
 
-			// Merge the results
-			if result, ok := resultsByStep[stepName]; ok {
-				result.Passed = append(result.Passed, stepResult.Passed...)
-				result.Rejected = append(result.Rejected, stepResult.Rejected...)
+			stepResult := step.validateAttestations(collections)
 
-				resultsByStep[stepName] = result
+			// We perform many searches against the same step, so we need to merge the relevant fields
+			if resultsByStep[stepName].Step == "" {
+				resultsByStep[stepName] = stepResult
+			} else {
+				if result, ok := resultsByStep[stepName]; ok {
+					result.Passed = append(result.Passed, stepResult.Passed...)
+					result.Rejected = append(result.Rejected, stepResult.Rejected...)
+					resultsByStep[stepName] = result
+				}
 			}
 
 			for _, coll := range stepResult.Passed {
@@ -325,6 +325,13 @@ func (p Policy) verifyArtifacts(resultsByStep map[string]StepResult) (map[string
 	for _, step := range p.Steps {
 		accepted := false
 		if len(resultsByStep[step.Name].Passed) == 0 {
+			if result, ok := resultsByStep[step.Name]; ok {
+				result.Rejected = append(result.Rejected, RejectedCollection{Reason: fmt.Errorf("failed to verify artifacts for step %s: no passed collections present", step.Name)})
+				resultsByStep[step.Name] = result
+			} else {
+				return nil, fmt.Errorf("failed to find step %s in step results map", step.Name)
+			}
+
 			continue
 		}
 
diff --git a/policy/step.go b/policy/step.go
index 1dae6fd7..5cd5630d 100644
--- a/policy/step.go
+++ b/policy/step.go
@@ -184,7 +184,7 @@ func (s Step) validateAttestations(collectionResults []source.CollectionVerifica
 		if passed {
 			result.Passed = append(result.Passed, collection)
 		} else {
-			r := strings.Join(reasons, "\n - ")
+			r := strings.Join(reasons, ",\n - ")
 			reason := fmt.Sprintf("collection validation failed:\n - %s", r)
 			result.Rejected = append(result.Rejected, RejectedCollection{
 				Collection: collection,
diff --git a/source/memory.go b/source/memory.go
index ee40f43e..8f7450e7 100644
--- a/source/memory.go
+++ b/source/memory.go
@@ -22,7 +22,6 @@ import (
 	"os"
 
 	"github.com/in-toto/go-witness/dsse"
-	"github.com/in-toto/go-witness/log"
 )
 
 type ErrDuplicateReference string
@@ -32,7 +31,6 @@ func (e ErrDuplicateReference) Error() string {
 }
 
 type MemorySource struct {
-	searched                   bool
 	envelopesByReference       map[string]CollectionEnvelope
 	referencesByCollectionName map[string][]string
 	subjectDigestsByReference  map[string]map[string]struct{}
@@ -41,7 +39,6 @@ type MemorySource struct {
 
 func NewMemorySource() *MemorySource {
 	return &MemorySource{
-		searched:                   false,
 		envelopesByReference:       make(map[string]CollectionEnvelope),
 		referencesByCollectionName: make(map[string][]string),
 		subjectDigestsByReference:  make(map[string]map[string]struct{}),
@@ -107,13 +104,6 @@ func (s *MemorySource) LoadEnvelope(reference string, env dsse.Envelope) error {
 }
 
 func (s *MemorySource) Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
-	if s.searched {
-		log.Debug("skipping memory source search: already performed")
-		return []CollectionEnvelope{}, nil
-	} else {
-		s.searched = true
-	}
-
 	matches := make([]CollectionEnvelope, 0)
 	for _, potentialMatchReference := range s.referencesByCollectionName[collectionName] {
 		env, ok := s.envelopesByReference[potentialMatchReference]
@@ -135,6 +125,20 @@ func (s *MemorySource) Search(ctx context.Context, collectionName string, subjec
 			continue
 		}
 
+		// make sure all the expected attestations appear in the collection
+		attestationsMatched := true
+		indexAttestations := s.attestationsByReference[potentialMatchReference]
+		for _, checkAttestation := range attestations {
+			if _, ok := indexAttestations[checkAttestation]; !ok {
+				attestationsMatched = false
+				break
+			}
+		}
+
+		if !attestationsMatched {
+			continue
+		}
+
 		matches = append(matches, env)
 	}