diff --git a/policy/policy.go b/policy/policy.go
index 5ab2408e..b9c4981b 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 {
-			// 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])
+			// initialize the result for this step if it hasn't been already
+			if _, ok := resultsByStep[stepName]; !ok {
+				resultsByStep[stepName] = StepResult{Step: stepName}
+			}
+
+			collections, err := vo.verifiedSource.Search(ctx, depth, stepName, vo.subjectDigests, attestationsByStep[stepName])
 			if err != nil {
 				return false, nil, err
 			}
 
 			if len(collections) == 0 {
-				collections = append(collections, source.CollectionVerificationResult{Errors: []error{ErrNoCollections{Step: stepName}}})
+				continue
 			}
 
-			// Verify the functionaries
+			// Verify the functionaries and validate attestations
 			collections = step.checkFunctionaries(collections, trustBundles)
-
 			stepResult := step.validateAttestations(collections)
 
-			// 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
-				}
+			// Merge the results
+			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 {
@@ -325,13 +325,6 @@ 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/policy_test.go b/policy/policy_test.go
index 761237c5..3336b7b8 100644
--- a/policy/policy_test.go
+++ b/policy/policy_test.go
@@ -417,7 +417,7 @@ func newDummyVerifiedSourcer(verifiedCollections []source.CollectionVerification
 	return &dummyVerifiedSourcer{verifiedCollections}
 }
 
-func (s *dummyVerifiedSourcer) Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]source.CollectionVerificationResult, error) {
+func (s *dummyVerifiedSourcer) Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]source.CollectionVerificationResult, error) {
 	return s.verifiedCollections, nil
 }
 
diff --git a/policy/step.go b/policy/step.go
index 5cd5630d..1dae6fd7 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/archivista.go b/source/archivista.go
index 2f74f722..9048bb21 100644
--- a/source/archivista.go
+++ b/source/archivista.go
@@ -32,7 +32,7 @@ func NewArchvistSource(client *archivista.Client) *ArchivistaSource {
 	}
 }
 
-func (s *ArchivistaSource) Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
+func (s *ArchivistaSource) Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
 	gitoids, err := s.client.SearchGitoids(ctx, archivista.SearchGitoidVariables{
 		CollectionName: collectionName,
 		SubjectDigests: subjectDigests,
diff --git a/source/memory.go b/source/memory.go
index 8f7450e7..8d0a7bdf 100644
--- a/source/memory.go
+++ b/source/memory.go
@@ -22,6 +22,7 @@ import (
 	"os"
 
 	"github.com/in-toto/go-witness/dsse"
+	"github.com/in-toto/go-witness/log"
 )
 
 type ErrDuplicateReference string
@@ -103,7 +104,13 @@ func (s *MemorySource) LoadEnvelope(reference string, env dsse.Envelope) error {
 	return nil
 }
 
-func (s *MemorySource) Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
+func (s *MemorySource) Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
+	if depth > 0 {
+		fmt.Println("skipping memory source search")
+		log.Debug("skipping memory source search: already performed")
+		return []CollectionEnvelope{}, nil
+	}
+
 	matches := make([]CollectionEnvelope, 0)
 	for _, potentialMatchReference := range s.referencesByCollectionName[collectionName] {
 		env, ok := s.envelopesByReference[potentialMatchReference]
@@ -125,20 +132,6 @@ 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)
 	}
 
diff --git a/source/memory_test.go b/source/memory_test.go
index 1995cc09..5f1cbd32 100644
--- a/source/memory_test.go
+++ b/source/memory_test.go
@@ -304,7 +304,7 @@ func TestSearch(t *testing.T) {
 			}
 
 			// Run the search query on the MemorySource
-			got, err := s.Search(tt.searchQuery.ctx, tt.searchQuery.collectionName, tt.searchQuery.subDigest, tt.searchQuery.attestations)
+			got, err := s.Search(tt.searchQuery.ctx, 0, tt.searchQuery.collectionName, tt.searchQuery.subDigest, tt.searchQuery.attestations)
 			if (err != nil) != tt.wantErr {
 				t.Fatalf("MemorySource.Search() error = %v, wantErr %v", err, tt.wantErr)
 			}
diff --git a/source/multi.go b/source/multi.go
index 500fc587..7443d474 100644
--- a/source/multi.go
+++ b/source/multi.go
@@ -28,7 +28,7 @@ func NewMultiSource(sources ...Sourcer) *MultiSource {
 }
 
 // Search concurrently queries all sources and returns the combined results.
-func (s *MultiSource) Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
+func (s *MultiSource) Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error) {
 	results := []CollectionEnvelope{}
 	errors := []error{}
 
@@ -61,7 +61,7 @@ func (s *MultiSource) Search(ctx context.Context, collectionName string, subject
 		// Goroutine for querying a source and collecting the results or error
 		go func(src Sourcer) {
 			defer wg.Done()
-			res, err := src.Search(ctx, collectionName, subjectDigests, attestations)
+			res, err := src.Search(ctx, depth, collectionName, subjectDigests, attestations)
 			if err != nil {
 				errs <- err
 			} else {
diff --git a/source/source.go b/source/source.go
index 1aad2bbd..c2d0f990 100644
--- a/source/source.go
+++ b/source/source.go
@@ -31,7 +31,7 @@ type CollectionEnvelope struct {
 }
 
 type Sourcer interface {
-	Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error)
+	Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]CollectionEnvelope, error)
 }
 
 func envelopeToCollectionEnvelope(reference string, env dsse.Envelope) (CollectionEnvelope, error) {
diff --git a/source/verified.go b/source/verified.go
index fab6404b..54b7d2cf 100644
--- a/source/verified.go
+++ b/source/verified.go
@@ -31,7 +31,7 @@ type CollectionVerificationResult struct {
 }
 
 type VerifiedSourcer interface {
-	Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionVerificationResult, error)
+	Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]CollectionVerificationResult, error)
 }
 
 type VerifiedSource struct {
@@ -43,8 +43,8 @@ func NewVerifiedSource(source Sourcer, verifyOpts ...dsse.VerificationOption) *V
 	return &VerifiedSource{source, verifyOpts}
 }
 
-func (s *VerifiedSource) Search(ctx context.Context, collectionName string, subjectDigests, attestations []string) ([]CollectionVerificationResult, error) {
-	unverified, err := s.source.Search(ctx, collectionName, subjectDigests, attestations)
+func (s *VerifiedSource) Search(ctx context.Context, depth int, collectionName string, subjectDigests, attestations []string) ([]CollectionVerificationResult, error) {
+	unverified, err := s.source.Search(ctx, depth, collectionName, subjectDigests, attestations)
 	if err != nil {
 		return nil, err
 	}